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UNITED STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No. 918 

Contribution from the Bureau of Entomology, L. O. HOWARD, Chief 

in collaboration with the Federal Horticultural Board 

C. L. MARLATT. Chairman 



Washington, D. C. 



PROFESSIONAL PAPER 



April 19, 1921 



REPORT ON INVESTIGATIONS OF THE PINK 
BOLL WORM OF COTTON IN MEXICO 



By 

U. C. LOFTIN, Entomological Assistant, K. B. McKINNEY, 

Scientific Assistant, and W. K. HANSON, 

Plant Quarantine Inspector 



CONTENTS 



Page 

The Laguna District 1 

Distribution of the Pink Bollworm .... 4 

Life History 5 

Seasonal History 19 

Feeding Habits of Larva; 21 

Damage Caused by the Pink Bollworm . 24 
Food Plants 32 

/ 



Page 

Dispersal 34 

Natural Control 38 

Repression 47 

Summary 5^ 

Literature Cited 57 

Appendix 58 




WASHINGTON 

GOVERNMENT PRINTING OFFICE 

1921 



LIBRARY OF CONGRESS 






Uu 



UNITED STATES DEPARTMENT OF AGRICULTURE 




BULLETIN No. 918 

•Jjfv, Contribution from the Bureau of Knlomology 

^' - L. O. HOWARD, Chief, in collaboration with the Federal 
Horticultural Board, C. L. MARLATT. Chairman 




■J^^'^^d. 



Washington, D. C. 



PROFESSIONAL PAPER 



April 19, 1921 



REPORT ON INVESTIGATIONS OF THE PINK BOLL- 
WORM^ OF COTTON IN MEXICO. 

By U. C LoFTiN, Entomnlofiical Aasislaat, K. ]'>. McKinney, Sclcmtijic Assistcmt, 
and W. K. Han.son,- I'hmt (JiKirdiUine Inspector. 



CONTENTS. 

Page. 



The Laguna district I 

Distribution of tlie pink Iwllworm 4 

Life liistory o 

Seasonal history 19 

Feeding habits of larviB 21 

Damage caused by the pink bollworm 24 

Food plants 32 



Dispersal 

Natural control . 

Eepression 

Smninary 

Literature cited. 
AppendLx 



Page. 
34 

38 
47 
50 



THE LAGUNA DISTRICT. 

In 1918 the Federal Horticultural Board deemed it advisable to 
establish a research station in a locality where there was a sufficient 
infestation of the pink bollworm to make possible the gathering of 
detailed information regarding this serious cotton post. This research 
station was established in February, 1918, in Ciudad Lerdo, Durango, 
Mexico, near Torreon. Approximately 95 per cent of the upland 
cotton produced in the Ilepul)lic of Mexico is grown in tliis vicinity, 
the so-called Laguna district. 

1 Pectinophora gossypiella Saunders: Order Lepidoptera, family Gelechiidae. 

2 This report is based on two years' work in the Lasuna, conducted by the Federal Horticultural Board 
under authority given , in the appropriation for the eradication of the pink bollworm , to investigate in Mexico 
or elsewhere the pink bollworm as a basis for control measures. The experts conducting this investigar 
tion were transferred to the Board for this purpose from the Bureau of Entomology and this paper is there- 
fore offered for publication as a joint contribution from these two offices. Provision for the establishment 
of the laboratory in Mexico and authority for the work was obtained through the courtesy of Senor Pastor 
Rouix, Secretary of Agriculture of Mexico. The work was made possible also by the active cooperation 
and assistance of the cotton planters of the Laguna. Special thanks are extended to the Tlahualilo Com- 
pany, the Testamentaria de Carlos Gonzales, and to Mr. Lloyd Rone for the use of their plantations for 
experimental purposes and many other courtesies. This station was established daring 1918 imder the 
general field direction of Mr. August Busck and was continued by the authors of this paper under the 
general direction of the chairman of the Board and Dr. W. D. Hunter. 

11696°— 21— Bull. 918 1 



BULLETIIS" 918, U. S. DEPARTMEXT OF AGEICULTUEE. 



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The Lagiina district is an irregularly shaped valley of about 2,000 
square miles, almost completely surrounded by mountains. It is 
situated about 250 miles south of the Rio Grande, on the boundary 
line of the States of Durango and Coahuila, Mexico. It derives its 
name from the fact that it was formerly a lake (laguna) serving as 
an outlet of the Rio Nazas. As recently as 1837 a part of the Tla- 

hualilo property was 
under water and at 
present there are con- 
siderable areas near 
San Pedro, Coahuila, 
which are filled with 
water when the river 
is at a flood stage. 
The soil is a deep al- 
luvial deposit, very 
rich, and well adapted 
to the culture of 
cotton. 

CLIMATIC CONDITIONS. 

Torreon, the prin- 
cipal city of the Lagu- 
na, has an elevation 
of about 4,000 feet. 
Generally spealdng, 
this section of the 
country receives an 
average of 6 to 8 in- 
ches rainfall annually, 
but in 1919 the pre- 
cipitation was very 
close to 15 inches. 

In the months of 
May, June, July, and 
August temperatures 
range from 95 °to 100° 
F. during the day 
down to about 64° (average) at night. In the winter months 
of December, Januar}'-, and February the thermometer registers from 
69° (average maximum) to as low as 24° F. 

Figure 1 gives a graphic record of the thermometer readings taken 
at the station in Ciudad Lerdo, Durango. 

It must be kept in mind that the above charts represent the aver- 
age of the daily readings for each month and not the extremes which 



zo 



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A 




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y 


X 


















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Fig. 1. 



-Average mean temperature for 191S and 1919 at 
Ciudad Lerdo, Durango, Mexico; 



PINK BOLLWORM OF COTTON IN MEXICO. 3 

were readied. Tlie relative humidity is rather high, often reaching 
the saturation point at night. 

From montlily records kept hy the Tlahuahlo Co., at Tlahuahlo, 
Durango, covering a period of 15 years extending from 1904 to 1918, 
inchisive, the average rainfall for that region has been 8.07 inches 
per year. 

Table I. — jhinual prrcipitntion in inches at Tlahualilo. 



Year. 


rreeipi- 
tation. 


Year. 


Precipi- 
tation. 


Year. 


I'recipi- 
tation. 


1904 

1905 


6.09 
11.31 
12.09 
8.71 
6.43 


1909 

1910 

1911 

1912 

1913 


13.32 
3.91 
6.98 
8.56 

12.79 


1914 

1915 


11.42 
4.63 
4.30 
3.46 
7.14 


190fi 

1907 

1908 


1916 

1917 

1918 



From records taken at the laboratory in Ciudad Lerdo, the fol- 
lowing figures arc given, covering the years 1918 and 1919, the years 
during which the observations relating to the pink bollworm in this 
report were made. 

Table II. — MonthJ;/ precipitation in inches at Ciudad Lerdo, Dnrango. 





Month. 


Precipitation. 




191S 


1919 


January . . ... 


(') 

(') 
0.35 

Trace. 
0.02 
2.76 

Trace. 
1.56 
0.07 
0. 09 
1.74 
0.21 


1 20 




Trace 


March 




54 


April 




00 


Mav 




00 


June 


1 44 


July 


3.98 




5 16 




1.75 




87 




0.15 






2 00 








Total 


6.80 


15 09 









Record onlv for Pec. 1-10. 



CULTURAL METHODS AND PRODUCTION. 



This section is semiarid and depends upon the water from the .Rio 
Nazas and Rio Agua Naval for irrigation. The water usually comes 
down some time between August and December and is applied at a 
rate which is equivalent to about 1 meter deep to the fields that are to 
be planted in the following year. With an occasional rain in June 
or July or a small amount of water from the river during these 
months the fall irrigation suffices for the crop. As there is not 
enough water for all the land, only a small portion is cultivated, and 
on some plantations a portion of the land regularly lies fallow for 
several years at a time. Under this system of cultivation the land 



4 BULLETIN 918, U. S. DEPARTMENT OF AGRICULTURE. 

has to be well prepared and thoroughly cultivated in order to con- 
serve the moistiu-e. The cotton planting begins about February 15 
and may continue until June if there are June rains or water in the 
river. The land is planted as soon as possible after it dries out, as 
this is necessary to secure germination. 

Cotton is the principal crop grown in this section, and while there 
are small areas devoted to corn, wheat, beans, and alfalfa, most of 
the planters use their land year after year for cotton and buy the 
feed for their domestic animals elsewhere. No very reliable data 
are available on acreage and production in the Laguna, but the an- 
nual production varies from 60,000 to 150,000 bales, with an aver- 
age crop of from 75,000 to 80,000 bales. The yield varies from one- 
fom'th bale to 2 bales per acre, vcith an average of from one-half to 
tluee-fom'tlis of a bale. All of the cotton is of the short-stapled 
varieties, as it has been found by experience that these give better 
results than the long-staple or Egyptian varieties. 

DISTRIBUTION OF THE PINK BOLLWORM. 

The species is widely distributed tlu"oughout the cotton-producing 
world, and according to Gough {12y is now known to occur in India, 
Palestine, Mesopotamia, Ceylon, Burma, Straits Settlements, Cliina, 
Japan, the Philippine and Hawaiian Islands, East i^rica, Zanzibar, 
Egypt, Sudan, West ^Vfrica (Southern Nigeria, Sierra Leone), Brazil, 
Mexico, and Texas in the United States. It has more recently been 
found in a limited an^a in western Louisiana adjoining the infesta- 
tion in eastern Texas. 

INTRODUCTION INTO MEXICO. 

The pink bollworm was- introduced into Mexico in 1911. During 
that season two importations of Egyptian seed were made. One 
consisted of 125 sacks and was planted near Monterey, in the State of 
Nuevo Leon. The other, consisting of 6 tons, was planted near San 
Pedro, State of Coahuila, in the Laguna district. From what is known 
of the abundance of the pink bollworm in Egypt in 1911 it is probable 
that both sliipments of seed were infested and that both of them con- 
tributed to the present infestation in Mexico. Cotton culture has not 
been continued in the vicinity of Monterey, but the crop of Egyptian 
cotton produced there in 1911 attracted considerable attention and 
much of the seed was shipped to the Laguna. 

At the present time the pink bollworm is generally and uniformly 
distributed in the Laguna. 

PRESENT DISTRIBUTION IN MEXICO. 

Outside of the Laguna district the pink bollworm is known to be 
established in tlu"ee localities in Mexico. One of these is at Santa 

3 Italic numbers in parentheses refer to " Liter iture cited," p. 57. 



PINK BOLLWORM OF COTTON IN MEXICO. 5 

Rosalia, State of Cliihuahua, at a point about 200 miles south of El 
Paso. The other two infestations are located in the northern portion 
of the State of Coahuila. One of these is at San Carlos, at a point 
about 15 miles southwest of the town of Jimenez on the Rio Grande, 
or about 40 miles approximately west of Eagle Pass. At this place 
infestation has been found in fields in the immediate vicinity of the 
gin. None of the insects were found in outlying fields. The other 
infestation in the State of Coahuila is located at Allende. This 
is about 40 miles from the nearest point on the Rio Grande. 

During the season of 1919 inspections were made by agents of the 
Federal Horticultural Board in the cotton region between Matamoras 
and Nuevo Laredo. No traces of infestation were found. Likewise 
the cotton growing in the Imperial Valley in the State of Lower 
California has been inspected with negative results. Inspecti(ui of 
these regions will be continued, as the insect may at any time be- 
come established along the Rio Grande by shijmKmts of seed from 
the interior of Mexico. 

Th(^ remarks above refer to infestations in growing cotton. The 
pest is frequently brought to the border towns of Mexico in cotton 
seed scattered in freight cars, and living specimens are constantly 
being found under such conditions by the inspectors of the Federal 
Horticultm'al Board. 

LIFE HISTORY. 

SUMMARY OF LIFE CYCLE, 

The motlis of the pink bollworm emerge in the eai'ly spring and 
summer from larvae which have passed the ^^^nter in cotton seed or 
bolls. The eggs are laid soon after emergence on almost any part of 
the plant. The incubation period is from 3 to 12 days and the larvae 
begin feeding in the squares or bolls. Dming the spring and summer 
the larval period occupies from 8 to 16 days, but in the fall and 
winter it is extended over a period of from, a few months to two years 
or more. These two kinds of larva\ while indistinguishable taxo- 
nomically, may be designated short-cycle or '^ summer" larvne and 
long-cycle or "resting" larva>. Pupation takes place in the soil or 
trash on the surface of the soil, in the summer stage, and in the 
ground, seed, or lint in the nesting larva\ The ])upal pc^riod covers 
from 6 to 20 days. The average length of the life cycle from egg to 
egg dm'ing the summer is '.U days. 

LABORATORY METHODS. 

The experiments with the life history of the pink bollworm were 
all conducted at Ciudad Lerdo, Durango, Mexico. An adobe house 
was used for a laboratory. The adults were confined in 2-quart 
fruit jars covered with cheesecloth for oviposition. Branches of 
cotton plants containing leaves and squares, stuck in tubes of water 



6 BULLETIN 918, U. S. DEPARTMENT OF AGRICULTURE. 

to keep them fresh, and bolls were provided for oviposition. Pieces 
of blotting paper dampened with water or sweetened substances 
were added as food for the moths. The eggs were removed to other 
jars for hatching and the young larvae carefully removed to the food. 
Bolls and squares were used, but the squares were found more 
satisfactory. The food with the young larvse was placed in vials 
plugged with cotton. The pieces of bolls would become discolored, 
decomposed, and unsuitable for food in one or two days, while a 
square would remain in good condition several days and the larva 
could be examined daily with less disturbance. 

Wire cages were also used over small potted plants and cotton 
plants in the experimental plat to check the laboratory results. 
The pupae were removed to glass vials with a piece of damp cotton 
in the bottom to provide the necessary humidity. 

Temperature and humidity records were made with maximum and 
minimum thermometers and recording hygro thermographs placed 
indoors and outside in a U. S. Weather Bureau instrument shelter. 

MOTH. 

Description. 

The moth with wmgs spread is about three-fifths of an inch from 
tip to tip, dark brown in color, with irregular blackish markings on 
the forewings, the hindwings silvery gray with no distinct markings. 
The forewings are bluntly pointed, the hindwings acutely pointed, 
and both heavily fringed posteriorly. When at rest the wings are 
folded flat over the back. 

Habits. 

The moths are very seclusive in their habits durmg the day. It 
is exceptionally rare to find one in the fields until after sundown. 
Just at dusk they can be seen flitting very quickly from plant to 
plant, and by close examinations with a flashlight at night they can 
be readily found in a resting position on almost any part of the plant. 
They are active as late as 12 p. m. No observations were ever made 
later at night, but it is very likely that they remain active until 
daybreak. Occasionally they conceal themselves on the plant, but 
usually they crawl under trash, stones, clods, or even into the loose 
soil. They are very loath to leave their hiding places during the 
day, but when disturbed they run with a quick jerky movement or 
fly a short distance and immediately hide under the nearest object. 

In the laboratory the moths emerging from stored cotton would 
congregate on the window screens at dusk. They would remain 
quietly till morning and then return to their hiding places. Only 
rarely would one be seen during the day. 



PINK BOLLWOEM OF COTTON IN MEXICO. 7 

Longevity. 

Males and females are produced in about equal proportions and 
their length of life is about equal. Under favorable laboratory 
conditions one moth was kept alive for 26 days, but the average 
length of life of tlic adult was 14.7 days. There are no indications 
that moths ever live for long periods of time or pass the winter in 
this stage. 

Wliether moths under natural conditions ever take nourishment 
other than water was never observed, but just as many eggs were 
deposited in the breeding jars where pure water was used as where 
sweetened water was substituted. Water is a very essential factor 
in the longevity of the adult. The average length of life of the 
moths where no water could be obtained was 7.G days, compared to 
14.7 days when water was supplied daily. 

Preovipositiox Period. 

Eggs were deposited in captivit}^ from 1 to 6 da\"s after issuance 
of the moth, with an average of 3.S days preoviposition period. It 
is not known how long a period elapses before oviposi- ^ -^ 

tion begins in nature, but from analogy with other species 
it is possible that the bulk of the eggs are laid the first 
night under normal field conditions. The moths were ' 
never observed in the act of depositing eggs, either in the 
fields or in the breeding cages, but from the night-flying 
habits of the moth it is evident that oviposition takes place ^^^i^x 
at dusk or at night. fig. 2.— Egg 

gQQ oi P ectino- 

phora gossy- 
DeSCRIPTIOX. picUa. Uigh- 

The egg is small, elongate oval, somewhat broader at 'y magnified. 
one end; length from 0.4 to 0.6 mm., breadth 0.2 to 0.3 mm.; shell 
iridescent, pearly white with greenish tint when first deposited, turning 
to almost red before hatching ; surface finely reticulated with regular 
longitudinal Imes or ridges with irregular cross-connections, resem- 
blmg the reticulations on the hull of a peanut. (Fig. 2.) The larva 
can be easily seen inside the shell just prior to hatching. 

PosiTiox ON Plant. 

The eggs are deposited on all parts of the plant, including the 
bolls and bracts, leaf buds, leaves, stems, and squares. The prefer- 
ence is for some more or less hidden location, such as the base of the 
boll, between the bracts and bolls, the folds of the small leaf buds, 
the creases formed by the veins and midribs of the leaves, and the 
axils of the leaves. 

Some heavily infested plants were examined at Lerdo during 
August and September, 1919, to determine the proportion of eggs 



8 BULLETIN niS, IT. S. DEPARTMENT OF AGKICULTURE. 

deposited on different parts of the plants, the results of which are 
given in Tahle III. 

Table III. — Location on the cotton plant of the eggs of P. gossypiella. 





Number and location of eggs. 


Total 


Number of plants 
examined. 


Leaves. 


Stems. 


Buds. 


Squares. 


Bolls. 


ninnber 

of eggs 

on 




Bracts. 


Base. 


Tip. 


plant. 




32 
21 
94 
31 
20 
22 


6 
6 
36 
36 
24 
16 
15 


45 
107 
34 
66 
37 
56 
17 


1 

3 

2 
3 
1 
3 


S 
11 
74 
54 
78 
93 

2 


81 
IDS 
87 
53 
49 
55 
39 



3 


1 
1 
2 



148 




270 




253 




315 




223 




243 




98 






Total (7 plants). 
Per cent 


227 
14.7 


139 
9.0 


362 
23.4 


13 

0.8 


320 
20.7 


472 
30.5 


7 
0.5 


1,549 







It is clearly seen that the boll is the most favored place, 51.7 
per cent of the entire number of eggs being deposited on the boll 
and its appendages. The small leaf buds were second with 23.4 
per cent, the leaves third with 14.7 per cent, the stems fom-th with 
9 per cent, and the squares fifth with only 0.8 per cent. It is fm'ther 
seen from this table that the base of the boll is frequently selected, 
as 30.5 per cent of the eggs were deposited there and only 0.5 per 
cent were deposited in the sutures at the tip of the boll. The 
position of the eggs upon the plant is important, for upon it largely 
depends the fate of the young larvae It is essential that the larvte 
reach the squares or bolls to feed, as no larva? were ever found which 
had developed beyond the second instar on other parts of the plant. 
It is a mistaken instinct of the moths to oviposit in other parts of 
the plant, as it is evident that a much larger proportion of the larvse 
hatching from eggs laid in close proximity to the food will reach it 
than of those that have to crawl over the plant exposed to their 
natm-al enemies in search of food. 

When laid on the leaves, buds, stems, and squares the eggs are 
usually placed singly or in small groups of from 5 to 10. When 
laid on the tip of the boll they are placed singly or in small groups 
in the sutm-es. In this position the eggs are often flattened or 
crushed by the growmg of the boll. When laid at the base of the 
boll they are placed between the calyx and the boll or beneath the 
bracts around the l)ase of the boll, and are usually in masses of 
from a few to as many as 75 to 100, which are overlapped and 
flattened out more or less shingle fashion. The flattened appear- 
ance in this case is due to the presence of the calyx and not to the 
natural shape of the egg. In these masses, eggs of all stages of 
development, as well as shells, are found, showing that they were 
not all deposited at one time by a single female. 



PINK BOLLWORM OF COTTON IN MEXICO. 



9 



As the female does not deposit eggs readily in captivity, diffi- 
culty was experienced in determining exactly how many eggs 
were deposited by a single female. In our experiment usually 
from 5 to 20 moths were confined in one cage. Under these con- 
ditions it was never Ivnown which moths had oviposited and 
which had not, and wliile several hmidred eggs were often obtained 
from a cage, it is certain that the maximum number they were 
capable of laying were never obtained. Often heavy, pregnant 
females were found dead in the cage and apparently never had 
deposited any eggs. Upon dissection of gravid females the ovaries 
were found to contam from 75 to 125 well-developed eggs. Busck 
(S) places the number at over a hundred and Willcocks (7) says that 
while small individuals may produce only about 250 eggs, well- 
developed individuals are capable of laying 400 to 500 eggs or more. 



Incubation. 

All of our records were made under laboratory conditions. 
.3 shows that the dif- 
ference between the 
maximum and the 
minimum, or the day 
and night tempera- 
tures, for each month 
amoimts only to from 
6° to 8° F. 

The egg stage, even 
under these rather 
constant conditions, 
varied from 3 to 12 
days. The range for 
the months of April, 



Figure 

























































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JAN. FS:B. Mf)R. APR. MRY JUME JULY f)U0. SEPT. OCT. NOU. 



Mav Sentember and ^^^' 3-— Average mean maximum and average mean minimum 
r^ ^ \ » ' „ temperatures for 1919 at Ciudad Lerdo, Durango, Mexico. 

October was trom 7 

to 12 days, and for June, July, and August it was from 3 to 5 
days, with an average of 4.6 days for the entire season, the average 
bemg taken from 300 records based on thousands of eggs. 

Hatching. 

The actual hatching of the egg requires only a very short time. 
The young larva can be seen moving inside the shell a short time 
before it actually emerges. An opening is cut in the broad end of 
the egg and the small larva wiiggles out and crawls rapidly away 
in search of food. 

The empty shell is white and soon becomes an almost unrecog- 
nizable wrinkled object. It remains on the plant until it decays or 
is carried away by the wind or other agencies. 
11696°-21— Bull. 918 2 



10 BULLETIN »18, U. S. DEPARTMENT OF AGRICULTURE. 

LARVA. 

Newly-IIatched Larvte. 

The newly-hatched Larvte are creamy white, with dark-brown 
head and thoracic shield and long, prominent, dark setje showing 
very plainly. They are a little less than 1 mm. in length and grad- 
uall}^ taper from the head, having thus a slight wedge-shaped appear- 
ance. In this stage the larvae are very active. Under laboratory 
conditions they are very restless and crawl rapidly from place to 
place before entering a square or boll. Many larva? continue crawl- 
ing around for 24 hours or more until they become so weakened that 
they are not able to cut their way into the squares or bolls. It was 
often observed that most of the larva^ which succeeded in entering 
the food provided for them did so the day they were hatched. It is 
not known to what extent this wandering around takes place under 
natural conditions. Larvae are found crawling over the plants, but 
they always seem restless and ill at ease. This probably does not 
take place normally to any great degree, except in the case of larvae 
from eggs laid on other parts of the plant than the squares and bolls. 

Larv^ Entering Bolls. 

Tlie larvae do not seem to have any preference as to where the boll 
is entered. Sometimes a light netlike web is spun and the entrance 
is made underneath it. At other times the entrance is made wdth 
no protection whatever. The larvae cut the carpel away, throwing 
the fragments outside, very little if any being consumed. The time 
required for the larvae to enter may vary with the age of the boll, 
but it usually takes them from 20 to 40 minutes to become com- 
pletely hidden. If the boll is examined soon after they have entered, 
the holes are easily located by the surrounding frass, and although 
minute, can be seen with the naked eye. After 2 or 3 days the frass 
is blown away b}^ the wind or removed by other agents and the 
holes close up, leaving only brownish spots which are hard to dif- 
ferentiate from other discolorations on the boll. Then they can 
only be detected by a trained eye, and the only w^ay to be certain a 
boll is infested is to examine its interior. 

Larvae After Entering Bolls. 

After the boll has been entered the larvae become glassy white, 
soft, and sluggish. They so closely resemble the watery lint at this 
stage that they would be very easily overlooked, except for their 
dark heads and thoracic shields, which show as black specks against 
the lint. 

There are three molts, completing four larval instars or stages. 
The first stage lasts about 2 days; the second and third, 3 to 4 days 
each; and the fourth, 4 to 5 days,; thus the larval development is 



PINK BOLI^WORM OF COTTON IN MEXICO. 11 

completed in an average of 13.3 days in the summer larva*. The sec- 
ond and third instars resemble the first in general appearance, and 
it is usually in the fourth or last larval stage tliat the larva? change 
to the characteristic pink color from which the name "pink boll- 
worm" is derived. Sometimes the pink color appears in the third 
instar, especially if development has been retarded in some way or 
the larva has been exposed to the air. The coloring first appears as 
transverse pink lines on the dorsal side of the segments and diffuses 
and deepens till there is only a small whitish or flesh-colored line left 
between the segments. The color seems to be more pronounced in 
the larvae which reach maturity in the late summer or early autumn 
and is a very deep pink or dull red. The head and thoracic shield 
are reddish brown with dark-brown mandibles and anal plate. Tlie 
ventral si.de, legs, and prolegs are white to flesh colored, the legs and 
prolegs with brownish claws and crotches. The full-grown larva is 
cylindrical and measures about one-half inch in length. 

With the fourth stage the larva becomes very active again when 
disturbed and conceals itself as quickly as possible. A cocoon is 
spun attached to whatever object the larva is hiding in. The full- 
grown larva is never content outside a cocoon after it leaves a boll or 
seed. If it is taken from one cocoon it will immediately make another. 
How many times this will be repeated was not determined, but a 
perfectly healthy larva is rarely if ever found outside a cocoon, 
except when crawling from place to place. 



The pupa is whitish, with faint markings of pink when first formed, 

turning to a mahogany brown as it dries and to a darker brown 

before emergence. It measures 8 to 10 mm. in length by 2.5 to 3 

mm. in width. The surface is covered with a fine velvety pubescence, 

the posterior end terminating in a short, stout, upwardly pointing, 

hooklike process. 

Pupation of Summer Larv.e. 

Wlien the summer larva? have completed their feeding, they cut 
to the outside of the boll directly through the carpel wall from the 
last seed attacked and drop to the ground for pupation. 

This exit hole through the carpel wall is usually round and clean 
cut and can be easily recognized as having been cut from the inside 
of the boll. Plate II, A, gives a comparison of the entrance hole into 
the boll of the common bollworm, Chloridea obsoleta Fab., and the 
exit hole of the pink bollworm. The entrance holes of the common 
bollworm are larger, not so clean cut, and surrounded by a raised 
margin. They are not likely to be confused once both have been seen. 

In the case of the summer larvae, the holes made in the green 
cotton boll are always for the exit of the larva?, and not for the issuance 



12 BULLETIN 918, U. S. DEPAETMENT OF AGRICULTURE. 

of the motli. From an examination in 1919 of over 16,000 green 
bolls that averaged over 2.5 larvae per boll, not a single pupa or pupal 
skin was found. Should a larva cut a hole in a green growing boll 
for the issuance of the moth, this hole would probably close from 
proliferation before the pupal stage of 9.3 days is passed. 

Occasionally, in mature or dry bolls, as distinguished from green 
ones, more than a mere exit hole is cut when the larva reaches the 
carpel wall. The carpel tissues and the adjoining lint are cut away 
and an elongate pocketlike cavity is made large enough for the larva 
to become straightened out in its final preparation for pupation. 
When this is done a light cocoon is spun inside tliis cavity and a hole 
cut through the carpel wall to the outside. The last remaining parts 
of the carpel wall are not cut entirely out leaving an open hole, but 
the particles are held together and in place by a few fine strands of 
silk which are easily broken and pushed away when the moth emerges. 

The very fact that only a few larv» pupate in the bolls is con- 
clusive enough that there are other more favorable places for pupa- 
tion. These places are either on the ground or in the ground. If the 
moisture conditions are sufficient on the surface, they may spin a 
cocoon in the trash or on any convenient object, and pupate there; 
but if it is too dry and the soil is loose they may burrow as deep as 3 
inches below the surface, m^ake an earthern cell, line it with a very 
fine, tough cocoon, and pupate there. Dui'ing the summer a good 
many pupie are probably destroyed by cultivation, but when pupa- 
tion takes place in the ground, only the exit passage being destroyed 
and the pupa itself not molested, the moth may be able to escape 
because of its burrowing power. 

Fullaway (S) and Busck (8) found that in Hawaii pupation nor- 
mally takes place in the boll and only rarely in the soil or other 
places. Maxwell-Lefroy (2) found that in India pupation occurs in 
the boll or on the bracts or leaves of the cotton, and in unirrigated 
black cotton soil might be found in a crack of the dry soil. Will- 
cocks (7, p. 113) says that in Egypt — 

Pupation seems most often to take place on the ground under the fallen leaves, or 
in the fold of a dead leaf or again between two dead leaves, also on old bolls which have 
dropped or been broken off, and under or attached to small lumps of earth. In fact 
they may be looked for amongst any shelter of this kind. One situation was noted 
that seems to be especially favored by the larvae as a haven to pass the pupal stage, 
this was fiuTiished by the dead flowers wliich are of course very niunerous below the 
plants. 

In Mexico pupse were never found on the leaves or bracts under 
field conditions. When green bolls were picked and left in sacks the 
emerging larvae would sometimes hollow out a slight depression and 
pupate near the base of the boll, or they would pupate between the 
involucre and boll without making a depression, or spin their cocoons 



Jul. 918, U. S. Dept. of Agriculture. 



Plate I. 




Cotton Bolls Showing Characteristic Injury by the Pink Bollwori\ 



3ul. 918, U. S. Dept. of Agriculture. 



Plate II. 




A, On lelt, entrance liolu of i'li/Diidambsolcta. On right, exit hulesuf |nuk bollworm. (Himter. 




-B, Double seed formed by pink lioihvorm larvae: Above, holes made for issuance oi moth: middle, 
broken apart to show cavities; below, double seed inlact. 

PINK BOLLWORM. 



PINK BOLLWORM OF COTTON IN MEXICO. 13 

on the sides of the sack. The old flowers under the plants did not 
seem to be more favored than other bits of rubbish. 

The duration of the pupal stage of summer larva? from 150 records 
ranges from 6 to 14 days. There is considerable variation among- 
the individual pupae, some requiring 1 to 2 days more than others 
which pupated on the same night. 

Table IV summarizes over 300 complete records of the various 
stages of the pink bollworm at Lerdo, Durango, Alexico, during 1918 
and 1019. 

Table IV. — Duration in (hujs ofsunniirr sl'igi's of P. gossi/pulld. 

Average 

Egg stage 4. G 

Larval instars: 

First 2-3 

Second 3-4 

Third 3-4 

Fourth 4-5 

Total average 13. 3 

Pupal stage 9.3 

Preoviposition period 3. 8 

Total period from egg to egg 31. 

RESTING LARV^. 

In the preceding part the development of the different summer 
stages of the pink bollworm has been discussed. There is still 
another important phase of the life history — the long-cycle or resting 
larvae. It is in this stage that the species passes the winter when no 
food is available or when conditions are adverse in any way. It is 
also in this stage that the greatest dispersal by man takes place and 
only in this stage that any known control measm-es can be used. 

Beginning some time in August, when the temperature is still high 
and there is yet plenty of food available^ some of the larva? upon 
reaching maturity do not pupate at once, but remain wherever they 
are as f.ull-fed larvae. These larvae are identical in form with those 
that pupate and can not be distinguished from them. Wliat causes 
some larvae to do this and others to pupate as usual when reared 
under the same conditions is not known, but Willcocks (7) suggests 
it is probably some instinct inherited from the time when in its orig- 
inal natural habitat there were no food plants available to sustain 
the species over a long period of time. In November and December, 
when the temperature is lower and no food is available, all of the 
larvae develop this tendency and it is the exception rather than the 
rule for them to pupate. Thus in the Laguna this resting habit 
seems to be a combination of estivation and hibei-nation, for it begins 
while food is still available and the temperatuie high. In this sec- 
tion the average frost date is about November 20, and moths emerg- 



14 BULLETIN 918, U. S. DEPARTMENT OF AGRTOULTITRE. 

ing after this date would as a rule find no suitable places for ovi- 
position. 

Wlien a larva prepares to go into the resting stage it remains in 
the boll in which it has been feeding. Usually a tough, heavy co- 
coon is spun either in the lint, in a single seed, or two seeds are fas- 
tened together to form a "double seed." (PI. II, B.) The double 
seed is formed by eating away part or all of the contents of the two 
adjoining seeds and spimiing a strong continuous cocoon inside the 
cavities of the two seeds, which holds them firmly together and 
makes them difficult to separate. 

Part of these seeds go through the gin and come out intact, and 
finding double seed is sure evidence of pink-bollworm infestation. 

Often double seeds are formed in seed in different locks, the con- 
necting cocoon running through the hole made in the partition wall. 
This affords good protection for the larva, as it prevents the seed 
from falling to the ground and being exposed to excessive moisture 
and other agencies which are more detrimental to the larva on the 
ground than on the plants. 

When the cocoon is spun in the lint or a single seed the larva lies 
in a curled-up position and the cocoon is spun tightly around it, 
forming a spherical compact mass. Similar cocoons are formed in 
the ground or attached to any convenient object if larvae are removed 
from seed or lint. The cocoon fits so closely and is so tough that it 
is very difficult to remove without injuring the larva. It is very 
hard to detect a larva inside a seed, and the only sure way to tell 
whether the seed contains a larva is to examine the interior. Will- 
cocks (7) in writing about Egyptian cotton seed, which has a smooth, 
black coat and is not covered with lint, says the silken-covered en- 
trance hole can usually be seen with a lens. This, however, does not 
hold true for short-staple seed. 

Few data are available on the number and proportion of larvae 
fomid in the lint and in the single and double seed. Samples of cot- 
ton were hand-ginned and the number of larva? in single and double 
seed determined, but unfortunately no record was kept of the num- 
ber in the lint. It is possible that some of the larvae counted as in 
single seeds in the first and second picking samples were in the lint., 
but this did not occur in the samples of the thu-d picking. It will 
be noted that the sample for the third picking is from the 1918 crop 
and had been stored for some time. At the time of examination a 
considerable part of the larvae were dead, but this does not affect the 
proportion found in the single and double seed, and while the figures 
are not quite comparable, they at least give an idea of the number 
of larvae present at different times. The number of larvas found in 
the single and double seed for the different picks are given in Table V- 



PINK BOLLWOEM OF COTTON IN MEXICO. 



15 



T.VBLE V.- 



Niimhcr of pink hollivorm. larvx found in single and double seed of cotton 
picked af different dates. 





Pate 
jiicked. 


Pate 
exam- 
ined. 


Poulile seed. 


Single .seed. 


Weight of sample. 


Niunber 
double 

seed. 


Number 
of lar- 
va? in 
double 
seed. 


Per cent 
of total 

larvne 
in double 

seed. 


Number 

single 

seed 

damaged. 


Number 

of larvae 

in single 

seed. 


Per cent 
of total 

larva"' 
in single 

seed. 


First picking: 


1019. 
Aug. i 
Aug. (i 
Sept. 23 

Oct. 1(1 
Nov. 2 

1918. 
Pec. 3 
Pec. 10 


lOlil. 
Oct. 10 
Oct. 8 
Oct. 22 

Oct. - 
Oct. - 

Mar. 30 
Mar. 20 



'0 



30 
334 

ion 

30 






29 
30 

9.5 
20 






58 
50. G 

30 
33 


3S 
108 
150 

121 

■107 

715 

597 


2 
1 


100 


i pound. 


inn 




3 100 


Second picking: 


21 
23 

250 
53 


41 




43.4 


Third picking: 


70 




(17 







1 One pupa in lint, not counted in above. 

2 Two pupoe in lint, not counted in above. 

This table shows that no double seed was found in cotton from the 
first picking, that 57.3 per cent of the larvse were found in double 
seed from the second picking, and that the percentage fell to 31.5 
in the third picking. It is probable, however, that occasional double 
seeds are formed during August and September or in the first picking. 

Taking an average of these figures and reducing them to a 1 -pound 
basis, the number of larv?e per bale present in the seed from the 
diff"erent pickings can be calculated. It is thought that no live larvae 
pass through the gins in the lint, and that many of the larvae in the 
seed are driven out during the cleaning and ginning. It is certain 
that the large number found in seed when hand-ginned were never 
found in commercially ginned seed. 

Table VI. — Number of pink bollworta Jar v;e found per pound and the estimated number 
per bale in cotton from different pickings. 





Pouble seed. 


Single seed. 


Weight of sample. 


Numljei' 
double 
seed. 


Numl)er 
lar va- 
in 

double 
seed. 


Esti- 
mated 
number 
of lar- 
viv per 
bale in 
double 

seed. 


Per cent 
of total 

larvK 

in 
double 

seed. 


Number 
single 
seed 
dam- 
aged. 


Number 
larv.'e 

in 
single 
seed. 


Esti- 
mated 
number 
of lar- 
viT" per 
bale in 
single 

seed. 


Per cent 
of total 

larvae in 
single, 
seed. 


Esti- 
mated 
niunber 
of lar- 
\a? per 
bale in 
single 

and 
douldo 

seed. 


First picking: 

1 pound 

Second jiicking: 

1 pound 

Third i)icking: 

1 poimd 



43 
189 



39 
101 




58, 500 

241, .500 



56.5 
2S.5 


121 

392 

1, 749 



30 
404 


9,000 

4.5,000 

000, OCW 


100 
43.5 

71.5 


9, OOJ 
103, 5C0 
847, 500 



Gough (J), in one of his earlier publications, states that there are 
two generations of the hibernating larva^, the older generation con- 



16 BULLETIN 918, U. S. DEPARTMENT OF AGRICULTURE. 

sisting of full-fed worms and the younger the winter-feeding brood, 
which were not full-fed at the time of hibernation and continue 
developing slowly till about March. In a later publication (12) 
weighings of resting larvee were made from January to July and it was 
found that the weight constantly fell from February to July. He 
concludes that "the fall in weight does not necessarily demand the 
explanation that the larvae were fasting, but taken along with the 
known fact that many hibernating or sestivating larvse do not feed, it 
lends considerable weight to the probability of the larvae not feeding 
during their resting period." 

A very small proportion of the larvae have not completed their 
growth when the cotton is picked, and these continue feeding for a 
while before making their resting cocoon. In some bolls examined 
November 26, 1918, there was an average of 6.64 fourth-instars and 
0.03 third-instars per boll. After the resting cocoon is once spun 
no feeding takes place. If larvae are removed from the seeds in 
which they are resting, other seed will sometimes be hollowed out, 
but the contents are thrown to the outside and no actual feeding 
takes place. It sometimes happens that frost does not come in the 
Laguna till January or February, and it is probable that feeding 
continues longer than usual in such years. 

Duration of the Resting Stage. 

Larvae are capable of passing long periods of time in this quies- 
cent stage. Gough (5) found in seeds of Indian cotton which had 
been imported to Egypt larvae which were over 2 years old. Busck 
(8). in Hawaii compressed cotton seed into small bales and found 
live larvae in them for 18 months. Willcocks (7) stored a large 
number of bolls, picked in November, 1913, in an outdoor cage, and 
moths continued emerging till August 28, 1915, a period of nearly 
2 years. There were, 4.4 per cent of the larvae in double seed col- 
lected in November, 1918, still alive on November 20, 1919, when 
work at the station was discontinued. 

Pupation of Resting Larv^. 

When the resting stage has been passed in the lint, single seed, or 
in any place where the larva is curled up in a small, compact cocoon, 
it is necessary to leave this cocoon and prepare more ample cjuarters 
for pupation. In such cases a lighter, more elongate cocoon is usu- 
ally spun among the fiber or seed, but in some instances in stored 
seed pupae are formed without any protection whatever. 

When the resting stage has been passed in the double seed the con- 
struction of the cocoon between the two seeds makes it elongate 
enough for the larva to pupate successfully and pupation usually 
takes place in, situ. In such cases the emergence hole for the moth 



PINK BOLLWORM OF COTTON IN MEXICO. 17 

is cut just prior to pupation and not when the seeds are first webbed 
together. Often the end of the pupal shell is seen protruding from 
the seeds through this opening. 

When pupation occum in old bolls of cotton a favorite method is 
to niake a slight depression in the lint and pupate between the <-ot- 
ton and boll. Where hibernation has been in the fields larvse may 
leave the bolls and pupate in the ground. On March 14, 1919, Ih 
square yards of soil in the corral at Lerdo, where many bolls were 
lying around, were examined. Four live larvae and one dead one, 
together with one live pupa and sevei'al empty pupal cases, were 
foimd. All were near the surface, one larva being under a piece 
of trash and the othei-s an inch or so down. All the larvae and 
the live pupa had light cocoons and seemed to have gone into the 
soil ft)r pupation rather than hibernation. In the case of the old 
pupal skins it could not be determined whether they came from 
hibernating larvae or were left over from the previous summer. 

The duration of the pupal stage from 250 resting larvge ranged 
from 8 to 26 days, with an average of 10.3 days. This is an average 
of 1 day more than for the summer larvae, due to the fact that pup- 
ation took place during the colder months. There is considerable 
individual variation in the length of pupae formed at the same time, 
but this occurs in pupae from summer larvae as well as from resting 
larvte. The puptie from, which male moths emerged required an 
average of one-half day more than those from which females emerged, 
the males requiring 10.5 days and the females 10 days. 

Time op Emergence from Resting Larv^. 

A few moths may emerge throughout the year in the Laguna. 
When work was first begun in the early part of February, 1918, 
freshly formed pupae were found among seed at the seed warehouses. 
During the month of March, 1918, there emerged 23.5 per cent of all 
the moths which emerged dming the year from larvae collected in 
seed in February and removed to the laboratory. Emergence con- 
tinued till August, when all of the lai'vae had died or emerged, the 
maximum being reached in May. Pupge were formed from larvae 
collected in the summer and fall of 1918 throughout the fall and 
into January, 1919, thus completing the cycle of pupation for every 
month in the year. The pupal period is greatly retarded during the 
cold months, but this does not prevent emergence on warm days. 
Table VII shows the monthly emergence of moths from resting 
larvae for 1918 and 1919. 

11696°— 21— Bull. 918 3 



18 BULLETIN 1>18, U. S. DEPARTMENT OF AGEICULTURE. 

Table VII. — The monthly emergence of moths from resting Jarvx for IDIS and 1919. 





1918 


1919 


Mouths. 


Number of 

moths 
emerged. 


Percent of 
total emer- 
gence. 


Number of 
moths 
emerged. 


Per cent of 
total emer- 
gence dur- 
ing period, 
covered. 




3S1 
236 
525 
355 
105 
16 


23.5 
14.6 
32.5 
21.9 

6.5 
1.0 


1 

125 

851 

1,811 

2,302 

708 

84 

40 

8 


(■) 
2 1 


April 


Mav 


14.3 




30.6 


July.... 


38.8 




12.0 


September 


1.4 


October 






.7 








.1 










Total 


1,618 


100.0 


5,930 


100.0 







1 No complete record. 

Moths emerging in 1918 were from larvae collected in seed in 
February, 1918; those emerging in 1919 were from larvie collected 
in bolls dm-ing November, 1918. Complete records are not available 
for Decem])er, 1918, or January, February, and March, 1919, due 
to absence from the laboratory. The i)ercentages of moths emerging 
each month are based on the total number of moths which emerged 
and not U])on the total number of larvae. Of the larvae collected in 
November, 1918, 4.4 per cent were still alive and had not pupated 
on November 20, 1919, when the records were discontinued. 

A study of Table VII shows that emergence took place much earlier 
in 1918 than in 1919. During March, 1918, 23.5 i)er cent of the 
moths emerged and the maximum of 32.5 per cent was reached in 
May, while in 1919 only 2.1 per cent emerged in April and the maxi- 
mum of 38.8 per cent was not reached till July. This seasonal 
variation depends largely upon the temperature and humidity. 
The winter of 1917-18 was unusually mild and there was an excep- 
tionally hot period during the first week of March which hastened 
pupation. It was also found that dampening the seed or lint hast- 
ened emergence and a rain followed by warm weather in March 
or April would no doubt cause large numbers to emerge. As a rule, 
moths emerging before the first of May would find no suitable places 
for oviposition and would not be a factor in starting the infestation 
in the following crop. 

ISSUANCE OF MOTH. 

The issuance of the moth from the pupal skin requires a very 
short time. The pupal skin breaks or splits along the dorsal side 
and the moth works its way out and crawls upon some object in the 
open so that the wings may develoj:) normally. As soon as the 
wings have extended to their fiill length they are raised and held 
in a vertical position from 5 to 15 minutes to become perfectly 



PINK BOLLWORM OF COTTON TN MEXICO. 



19 



dried. Aftei-ward the moth crawls off and hides until dark, if 
issuance has taken place during the da}'. Wliat course is followed 
when issuance takes place at night was never observed. 

Time of Day Moths Emerce. 

The moths emerge from the pup» at all hours of the day and 
night imder laboratory conditions, where the temperature and 
humidity are more or less uniform. From Table VIII it can be seen 
that between the morning examinations and the afternoon exami- 
nations, 421 moths emerged in 134. .5 hours, an average of 3.1 moths 
per hour, and that 348 moths emerged between the afternoon exami- 
nations and the morning examinations in 301 hours with an average 
of 1.1 moths per hour. About three times as many moths emerged 
during the day as emerged per hour during the night. 

Table VIII. — Time of day of emergence of the adidt 1'. (josityjnella. 



Date. 


Morning exami- 
nation. 


Afternoon exami- 
nation. 


Pate. 


Morning exami- 
nation. 


Afternoon exami- 
nation. 


Time. 


Numlser 
ofadults. 


Time. 


Niunber 
ofadults. 

27 
5 
17 
25 
27 
26 
13 
19 
25 
16 
15 
42 


Time. 


Number 
ofadults. 


Time. 


Number 
ofadults. 


1919. 
May 22 
May 23 
May 24 
May 25 
May 26 
May 27 
May 28 
May 29 
May 30 
May 31 
June 1 
June 2 


10.00 
9.30 
9.30 

10.30 
9. 30 
9.30 
9. 30 
9.30 
9. 30 

10. on 

10. 00 
9. 30 
10. 00 


16 

15 
10 
15 
17 
13 
11 
46 
20 
14 
13 


5. 25 
5.30 
5.30 
5.30 
5.00 
5. .30 
6.00 
8.30 
6.30 
8.30 
6.00 
5.30 


1919. 
June 4 
June 5 
J une 6 
J une 7 
June 8 
June 9 
June 10 
June 11 
June 12 
June 13 

Total 


10.00 
10. 00 
10.00 
10.00 
10.00 

10.00 

10. 00 
10.00 
10.00 
9.30 


(') 
22 
25 
14 

(') 

(') 
20 
26 
41 
8 


5.30 
6.00 
6.00 

{-) 

6.00 
5.00 
5.00 
5.30 


9 
19 
20 

(^) 
28 
39 
27 
22 




348 




421 


June 3 









1 All removed. 



' No record. 



SEASONAL HISTORY. 

The data show that moths may emerge at any time during the 
winter or early spring, and so far as known they may begin breeding 
if suitable food plants are found. Cotton does not grow as a peren- 
nial in this section. Sometimes it is left for the second year to pro- 
duce a ''zoca" crop, but tlie plants are dormant during the winter 
and the crop is produced from sprouts sent out from the roots or 
old stalks. Planting may begin during the first part of February, 
but usually begins about the middle, depending upon the season. 
Squares are not formed in any numbers until about the first of May, 
usually a little earlier on the zoca than on the plant cotton. Holly- 
hock, another host plant of pink bollworms, may be in bloom earlier 
than cotton, but it is considered of no economic importance in this 
connection. Repeated attempts to secure oviposition on young 



20 



BULLETIN 918, U. S. DEPARTMENT OF AGRICULTURE. 



cotton plants during March and April, 1918, were unsuccessful. 
The first eggs were laid in the breeding jars on May 5, and the first 
larva (one of the third instar) was found in cotton in the field on 
May 15, 1918. The first eggs were deposited on April 9, 1919, and 
the first larva found in the field on April 28. The general infestation 
in the fields, however, did not begin till later in 1919 than in 1918. 

In general, it may be said that breeding commences in the spring 
as soon as the squares begin to mature and by the time the first 
blossoms appear a few larvsB are present. The infestation is 
extremely light at this season and only by careful search will any 
larvae be found. As a rule the bolls are not attacked till they are 
from one-half to three-fourths grown, though occasionally a larva 
works down from the blossom to the newly set boll. It is usually 
about the middle to latter part of July before bolls on plant cotton 
are sufficiently mature to be attractive to the larvae. From this 
date onward the infestation rapidly increases, and in about 10 weeks' 
time practicaUy every green boll is infested. The cool nights of 
October and November check the development somewhat, but 
breeding continues until frost destroys the food plants. 

Table IX shows the weekly increase in the percentage of green 
bolls infested during the 10 weeks during which breeding is most 
active. It is computed from weekly examinations of samples of 
green bolls collected on different plantations, an average number of 
350 in 1918 and 1,100 in 1919 being used. 

Table IX. — The weekly increase in the percentage of green bulls infested with Pectino- 

phora gossypiella. 



Week ending — 



July 12. 
July 19. 
July 26. 
Aug. 2. 
Aug. 9. 
Aug. 16 
Aug. 23 



Percentage of green 
bolls infested. 



1.1 

7.0 
13.6 
20.0 
21.0 
42.0 
65.8 



4.3 
5.0 
10.8 



Week ending- 



Aug. 30. 
Sept. 6.. 
Sept. 13. 
Sept. 20. 
Sept. 27. 
Oct. 4... 
Oct. 11.. 



Percentage of green 
bolls infested. 



79.2 
93.0 
97.3 



20. S 
29.0 
41.0 
45.0^ 
63.0 
83.3 
100. Q. 



From Table IX it is seen that the time of active breeding varies 
considerably, and that in 1919 it was a month later than in 1918. 
This depends largely upon the development of the cotton. The same 
climatic conditions which retard the growth of the cotton also affect 
the activity of the species, and the relative development of the two 
is about the same from year to year. It is also clearly shown that 
there are no distmct broods or generations and that the heavy 
infestation in the fall is accumulative. If the offspring from moths 
emerging early in the spring continue breeding throughout the 



Bui. 918, U. S. Dppt. of Agriculture. 



Plate III. 




A, Characteristic rosette ajiiiearaiice uf cultuii flowers infesteil witli llie i)iiik bolhvorm. 




B, Holes cut throut^h partition wall when larva goes from one lock to another. (Hunter.) 
PINK BOLLWORM. 



PINK BOLLWOPtM OF COTTON IN MEXICO. 21 

season till December and make a complete life cycle every 31 days, 
there are six generations, but if the motks do not emerge from the 
restmg larvae until the fall and the firet generation goes into the rest- 
ing stage again, the whole year may be passed in only one generation. 

FEEDING HABITS OF LARV^. 

LARV^ FEEDING ON LEAVES AND STEMS. 

The feedmg of the pink bollworm on the leaves of cotton is of no 
economic importance. It is a forced condition rather than a voluntary 
one. If the eggs have been deposited a long way from the squares 
or bolls, the larvae may feed slightly on the leaves while searching for 
suitable food. In such cases slight abrasions on the surface of the 
leaf or minute pinholes through the leaf occur. The larvae feeding 
in this manner appear either to die for lack of sufficient nourishment 
or to be destroyed by other insects. No larva? older than those of 
the second instar were ever observed feeding on leaves and only 
two or three cases of the second instar. No indications of entrance 
into the bolls by larva^ of the second or later stages were ever 
observed under field conditions, except where the larva? had been 
feeding in blossoms and had worked downward into the newly set 
bolls. Willcocks (?) records larvte feeding in the stems of the 
plants just above the surface of the ground in Egypt, but this class 
of injury was never seen in the Laguna. 

LARV/E FEEDING IN SQUARES AND FLOWERS. 

The young larva> enter the squares by cutting directly through the 
undeveloped flower petals and feed on the pollen and fleshy parts 
of the embryonic flower, usually reaching the third or fourth instar 
by the time the flower opens. These infested flowere do not open 
normally, but have a peculiar rosette appearance which is well shown 
in Plate III, A. The tips of the corolla in infested flowers are 
webbed together by the larvae with fine silken threads which prevent 
their opening wide and exposing the larvae to the attacks of other 
insects and the heat of the sun. 

These infested flowers are easily distinguishable from normal 
flowers in walking through fields of upland or short-staple varieties. 
Even though the percentage of infested flowers was about the same 
in Egyptian or long-staple cotton the pronounced rosette effect was 
never seen. The corolla is longer and larger in Egyptian varieties 
and the threads spun by the larva probably are not sufficiently 
strong to prevent its opening. Wlien infested flowers are examined 
the larva is usually found beneath a fine silky web, covered with 
frass and pollen grains, and feeding upon the anthers. If full-fed when 
the flower opens it may leave it the first day and drop to the ground 
for pupation. This is especially apt to occur if the larva is dis- 



22 



BULLETIN 918, U. S. DEPARTMENT OF AGRICULTURE. 



turbed by other insects, such as the flower beetle, Euphoria lasalis 
Gorg. If the larva is not full-fed at the time of opening it may 
continue feeding inside the flower for two or three days or until 
after the flower has dropped, or it may work downward from the 
flower into the newly formed boll. No indication of the larva leav- 
ing flowers and going into large bolls was ever observed, and it is 
exceptionally rare to find more than one larva in a single square or 
flower. From Jmie 1 till August 10, 1919, a daily record, with a few 
exceptions, was kept of the flowers opening on a small plot of heavily 
infested cotton at Ciudad Lerdo. The results are given in Table X. 

Table X. — Infestation of cotton blossoins by the pink bollwonn. 



Month. 



Number 

of 

days 

counted. 



Infested. 



Non- 
infested. 



Total. 



Percent- 
age 
infested. 



June... 
July. . . 
August 



226 
898 
967 



8,210 
12,333 
2,508 



8,436 
13,231 
3,475 



2.7 
6.8 
27.8 



On October 3, 50 per cent and on November 10, 90 per cent of the 
flowers on this same plot were infested. This plot was more heavily 
infested than is normally the case under field conditions. The in- 
festation is usually highest in June and July, when few large bolls 
are present on the plants, and decreases dming August and Septem- 
ber. In October and November, when there are many larvae pres- 
ent and not so many green bolls, the infestation again increases and 
the few blossoms appearing at this time are heavily infested. As 
the feeding in the squares and blossoms is largely on the pollen, 
the presence of a larva does not necessarily prevent a normal boll 
from forming. Blossoms were tagged in 1919 and it was found 
that 40.8 per cent of the noninfested squares and 67.6 per cent of 
the infested blossoms were shed. 

LARV^ FEEDING IN BOLLS. 

That inside the bolls is the most favored feeding place for pink 
boUworms is shown by the fact that as soon as the bolls are large 
enough most of the larvae choose bolls instead of squares or flowers. 
They attack the boll in all stages of its growth, from the time it is 
the size of a pea until it begins to open, though most commonly 
it is not entered until about one-half to three-fourths grown. The 
larviB bore into the boll at any point upon its surface soon after 
hatching and remain in the same boll mitil ready for pupation. 
Once the larvae have entered the boll no definite plan of procedure 
is followed. They may burrow directly through the carpel and 
begin feeding on the soft watery lint or they may stop before cutting 
completely through and burrow for an inch or more in the spongy 



PINK BOLLWORM OF COTTON IN MEXICO. 23 

carpel tissues just beneath the inner wall of the boll. In the latter 
case they leave brownish, discolored tunnels or burrows resembling 
the work of young leaf miners. These tunnels, commonly called 
"railroads," are very characteristic of pink boUworms and when 
found are sm'e evidence that a boll is infested. They disap]>ear as 
the boll grows older and are not noticeable in an open boll. 

When the larva* cut directly through and into the lint sometimes 
a slightly discolored proliferation resembling a puncture made by 
a cotton stainer is formed and at other times only a slight discolor- 
ation is left. Again, a larva may be found inside a boll and no sign 
of its entrance place found even when the boll is examined from the 
inside. The larva? may tunnel in the carpel tissues or feed in the lint 
in any direction from the point of entrance and seldom if ever feed 
on seed until after the first molt. Tliey may burrow between or 
cut through the fibers of the lint for a considerable distance while 
feeding on the soft tissues, leaving behind slightly discolored trails 
through the lint and "railroads" through the immature seed coats; 
or, on the other hand, they may remain feeding on the lint near the 
point of entrance. 

Second or third instar larva? are found which seem to have fed 
exclusively on the lint, but there is always some feeding on the seed 
])efore the lai"va? become fully mature and second and third instars 
are frequently found in the seed. The seeds are normally first 
attacked from the broad end nearer the outer sm^f ace of the boll. The 
contents of the first seed attacked are not eaten completely out 
before an adjoining seed is attacked. The num])er of seeds attacked 
by a single larva varies greatly, due to the age and development of 
the boll at the time of attack and the behavior of the larva. Cases 
have been seen where a larva completed its development on as few 
as two seeds and within a short distance of the place of entrance, 
while another larva may destroy a whole lock or more. Often a 
larva will cut through the partition into the adjoining lock instead 
of going to another seed in the same lock. The hole in tlie partition 
is clean cut, round or oval, and is good evidence that a pink l)()llworm 
has been in that boll. Plate III, B shows these holes. 

When very small bolls are attacked by larvse working downward 
from the flowers, they turn brown and usually drop from the plants, 
but if the bolls are not attacked till about half grown, the presence 
of larvoe does not cause them to shed. When there are only 2 to 4 
larvae in a boll that is rather far advanced, say three-fom-ths to full- 
grown, when attacked, the work may be classed as ''clean," but if 
several larva? have attacked a })oll that has not reached that stage, 
the entire contents are very likely to be com^^letely broken down 
into a decayed mass. The presence of larva? in Ixdls does not prevent 
other larvae from entering, and usually larva? of all stages are found 



24 BULLETIN 918, U. S. DEPARTMENT OF AGRICULTURE. 

in the same boll. During the latter part of the season, when the 
infestation is heavy, an average of 6 or 7 larvae is found per boll and 
individual l)olls may contain many more. One boll was examined 
that contained 26 larvae. The number for all bolls examined through- 
out the season of 1919 averaged 2.5. 

PROLIFERATION OF BOLLS. 

The presence of larva? often causes the bolls to form abnormal 
growth or proliferation. Proliferation is described by Dr. W. E. 
Hinds (1) as: 

The development of numerous elementary cells from parts of the bud or boll wliich 
are themselves normally the ultimate product of combinations of much more liighly 
specialized cells. The resulting product is thus composed of comparatively large, 
thin-walled cells, which are placed so loosely together that the resulting formation is 
of a soft textiu-e, and has a granular appearance which may be plainly seen with the 
unaided eye. 

Greenish white or discolored brownish opaque swellings are formed 
on the inner wall of the carpel, the seeds themselves proliferate, 
and very little if any lint is formed on them. This spongy mass of 
granular cells develops much more rapidly than lint, thus occupying 
the space that would have been filled with lint. Badly proliferated 
bolls contain but little lint, and this is matted or felted and of poor 
quality, thus greatly increasing the damage done by the pink boll- 
worms. Proliferous seeds are not confined to tliose actually attacked 
by the larva^. The irritation caused by the presence of the larvae in 
a boll or the stimulation from proliferation in seed actually injm'ed 
causes other healthy seed to proliferate. The percentage of proliferous 
bolls increases very rapidly with the advance of the season, which is 
simultaneous with the in(Tease of the number of bolls attacked by 
the pink bollworm and with the number of larvae in each boll. The 
Egyptian cotton grown at the laboratory was much more severely 
affected by proliferation than were the short-staple varieties. Larvae 
occasionally are killed by proliferation, but from general observa- 
tions it is thought that not more than one-tenth of 1 per cent are 
killed in this way. The result is by far more detrimental than 

beneficial. 

DAMAGE CAUSED BY THE PINK BOLLWORM. 

The damage by the pink bollworm is caused by the feeding of 
the larvae on the squares and blooms, the walls and partitions of 
the bolls, and the lint and seed of the cotton. Upon entering the 
boll after hatching the larvae feed on the lint and tender tissues of 
the boll during its earlier stages of growth; in the latter stages the 
larva? feed almost exclusively on the seed, thereby arresting the 
development of the lint and seed and also destroying the seed itself. 
In passing from seed to seed and from lock to lock the larvae cut and 



PINK BOLLWORM OF COTTON IN MEXICO. 



25 



discolor the lint. Just as soon as the bolls are formed they may he 
attacked by the larvte working downward from the flower, hut 
usually they are not attacked till one-half to three-fourths grown. 
The damage to the individual boll is greater the earlier it is attacked. 
In case the larva enters when the boll is very young, that is, one- 
half grown or less, the boll is usually completely destroyed. But 
when a boll is not attacked until it is about half grown an infesta- 
tion by a larva or even several larvae does not necessarily prevent 
the boll from opening and producing some pickable cotton. The 
cotton from infested bolls is of an inferior grade, the lint usually 
being short, hard, and kinky. The porticm of the boll actually con- 
sumed by the larva may be comparatively small, but the damage 
caused by the feeding habits and presence of larva? in a, boll amounts 
to a considerable percentage loss to the crop. The irritation pro- 
duced by the presence of a larva often causes proliferation to take 
])lace; and upon entering and leaving the boll the larva^ provide a 
means for the entrance of air and water, thereby causing decompo- 
sition in the green bolls. 

RELATION OF AMOUNT OF DAMAGE TO INCREASE OF INFESTATION. 

It has been estimated that the natural winter mortality of all 
insects is about 95 per cent or more. In addition to this, the number 
of pink boUworms in the cotton fields of the Laguna district is further 
reduced by the irrigation methods, fall burning of plants, and the 
grazing of the fields by cattle, goats, etc. It is obvious that at the 
beginning of the crop the infestation, even where it was general the 
previous year, would be very light, but as the number of larvae in 
the field increases the amount of damage becomes greater. 

The pink boUworm attack is not similar to that of other insects 
like the cotton leafworm, Alabama argillacca Hiibn., or bollworm, 
Cldoridea ohsoleia Fab., which practically ruin a crop overnight, but 
is more of a gradual, built-up attack, starting in the beginning of 
the crop with practically a negligible infestation and culminating 
with 100 per cent of the bolls infested with from 4 to 10 larva? in 
every boll. Table XI shows the rate of monthly increase of larvae 
in several averaw fields of the Laguna. 



Table XI. — Prorp-es.s of iiifcsfation In/ larrn' of Oic pink bnllvonii: luinihrr of himr per 

100 bolls. 





I'lantation. 




Month. 


Hormi- 
guero. 


Alvia. 


I,a('on- 
cha. 


San Isi- 
dera. 


Zara;,'osa. 


Hcsas. 


Barce- 
lona. 


Avenige. 


August.. 

Septemlier 

October 


2.6 

\m.Q 

710. 
f'20. 


15.3 
12.S. 7 
694.0 
790.0 


5.0 

93. 5 

5.S5. 2 

668. 


5.2 

62.7 
74S. 
638. 


32.6 
312.0 
773. 


33. 6 

210.7 
S07. 4 
MU. I) 


17.6 

ISS. 
496. 6 
464. 


15.9 
156. 
662. 9 




724.0 









-Bull. 918- 



26 BULLETIN 918, U. S. DEPARTMENT OF AGRIt'ULTUEE. 

The data in the foregoing table were compiled from records kept 
of weeldy examinations made of 100 boll (green) samples taken from 
different plantations in the Lagima disrict. The bolls in each sample 
were taken by walking tlu-ough the same fields each week and pick- 
ing the bolls at random. 

ESTIMATE OF DAMAGE TO LAGUNA CROP, 1919. 

In making an estimate of the damage caused by P. gossypiella to 
the cotton crop of the Laguna for 1919, it was thought best to select 
certain average fields on average plantations and to keep these 
particular fields under close surveillance during the entire year. 

Tlu'ough the com-tesy of Don Carlos Gonzales y Farino, of Torreon 
and of the Tlahualilo Company, Tlahualilo, Dm-ango, certain fields 
upon their properties were selected. These fields were chosen with 
the utmost care in order to obtain as nearly as possible an average 
of all conditions of the Laguna, with respect to factors controlling 
the amount of damage caused by P. gossypiella. Other fields in dif- 
ferent parts of the Laguna were examined as often as time would 
permit for comparison with these fields. Each of these fields was 
visited regularly (as far as conditions would permit) once a week, 
and samples of 100 green bolls taken, so that the rate of increase of 
infestation might be ascertained. 

Samples of seed cotton were also taken at the beginning of each 
pick from each of the experimental fields, to determine the damage 
caused by the pink bollworm in the different harvesting periods. 
These samples were ginned in a sample gin sepai'ately, accurate 
weights being kept of the quantity of lint and seed. A sample of lint 
from each field sample was taken for classification by the Bureau of 
Markets, United States Department of Agriculture, to determine 
the discolorations, grades, and spinning qualities of the lint. 

A 2-pound sample of seed was taken from each field sample for 
chemical analysis to determine quality and quantity of oil. 

DAMAGE TO SQUARES AND BLOOMS. 

The pink bollworms enter the squares just after hatching from 
the eggs, and continue feeding until they complete the larval stage, 
notwithstanding the fact that the squares may bloom in the mean- 
time. Larva3 of all stages have been found in the squares, but 
generally speaking only full-grown larvae have been observed in the 
blooms. To ascertain to what extent this floral feeding habit tended 
to cause damage the following experiment was carried on. 

Tags were placed on 343 normal blooms and on 343 infested blooms 
during June and July. Table XII shows the results. 



PINK BOTJ.WORINI OF COTTON IN MEXICO. 



27 



Table XII. — Results' of experiment to determine, damage caused hy feediiui of the pink 
bolJ'Worm in the blooms of cotton. 



Blooms. 


Number Propped 
of tags. off. 


Set l)oIls. 


Per cent of 
blooms 
dropped. 


Norrrml 


343 
343 


140 

232 


203 
111 


40 8 


Infested 


<i7 G 







From the ahove table it will be seen that 40.8 per cent of the normal 
blooms did not set bolls, but 67.6 per cent of the infested hlooms did 
not set bolls, a difference of 26.8 per cent. Grantino; that under 
favorable conditions the natural tendency of the plant will be to 
reset these fruits, it is obvious that 26.8 per cent of the blooms will 
make bolls at a much later date than they normally would, thereby 
subjecting them to a far heavier infestation, hence a greater amount 
of damage. The later maturity of the crop due to shedding of the 
early squares would also greatly increase the damage by the boll 
weevil in countries where this insect is present. (See Table XI 
on "Progress of infestation. ") 

The rate of monthly increase of the infested blooms in a given 
field is shown in Table X. 

DAMAGE TO BOLLS. 

In estimating the damage caused to the mature bolls (PI. I), 
pickable as well as nonpickable cotton must bo considered. By 
pickable cotton is meant cotton that is picked, ginned, and marketed 
from the beginning to the end of the crop; by nonpickable cotton, 
the bolls or j^xH'tions of bolls that are left on tlie plants as mafit for 
picking, due to damage by the pink bollworm. 

PICKABLE COTTON. 

To arrive at a conclusion as to the extent the cotton taken from 
the fields is damaged, a 100-poimd sample of seed cotton was taken 
from each picking in each experimental field. These samples were 
taken by picking all the open cotton on about every twentieth 
plant in each row, in this manner obtaining as nearly as possible a 
composite average sample of the cotton open in the field on that 
date. After the sample was taken the remaining open cotton was 
picked in the customary manner, thereby guai'ding against the 
possibility of mixing any of the firet and second pick cotton in the 
taking of the later samples. 

The samples were stored until the end of the season and then 
ginned separately, using a small 10-saw sample gin. A gin sample 
of approximately 2 pounds of lint and a sample of seed weighing 
about 2 pounds were taken from each of the field samples at the 
time of sinnino;. 



28 



BULLETIN 918, U. S. DEPARTMENT OF AGRICULTURE. 



Loss IN THE Quality of Lint. 

Tlie 2-poiin(l gin samples were sent to the United States Bureau 
of Markets for examination. Mr. George Livingston, Chief of 
Bureau, reported in letter dated April L3, 1920, as follows: 

In a general way it may be stated that all of the samples were of ver\ poor (jiiality, 
especially as regards length and strength of staple. The results ol)tained through 
the ordinary commercial classification of cotton were confirmed by individual fil)er 
strength tests which i^roduced subnormal results. It is commonly considered that 
ui^land cotton should show an average strength for indi'vidual fibers of about 8 
grams, but none of the Mexican samples possessed that degree of strength. Several 
of the samples were so weak that a considerable portion of the libers broke upon being 
inserted in the jaws of the testing machine. Such cotton is so weak in staple as to be 
practically unspinnable. 

The exact degree of the deterioration in the quality of lint men- 
tioned above which is due to the pink boUworm can not be definitely 
stated, but undoubtedly a certain percentage of it is caused by mal- 
nutrition of the seed, which arrests the development of the lint. 
Ballou {11 J p. 265) states: 

In addition to the actual damage done to the lint and seed of the attacked seed, 
there is the injury which results to sound seed in attacked bolls. This appears to be 
a matter of malnutrition, the attacked seed making demands on the supply of the 
plant food to such an extent that nearly all the seeds in the boll are deprived of a 
portion of their nutriment. 

Loss IN Weight of Seed. 

As the amount of seed destroyed or practi(;ally destroyed by 
P. gossypiella was found to assume proportions worthy of consider- 
able notice, an attempt was made to ascertain the exact loss by 
weight caused in this manner. From material picked dm'ing the 
year, samples of seed cotton were accurately weighed, hand-ginned, 
and the seed examincnl individually and weighed, with the following 
results : 

Table XIII. — Loss by wekjhi to ficcd vhrn luind ginned. 





Weight 
sample. 


Total 
num- 
ber 
seed. 


Sound seed. 


Damaged seed. 


Lint. 


Sample. 


Num- 
ber of 
seed. 


Weight 

in 
grams. 


Aver- 
age 

weight 
per 

seed in 

gram. 


Num- 
ber of 
seed. 


Weight 

in 
grams. 


Aver- 
age 
weight 

per 
seed in 
gram. 


Ivossiii 
weight 

per 
seed m 
gram. 


Weight 

in 
grams. 


Per 

cent. 


First pick,Zara- 

gosa. 
Second pick, 

Zaragosa. 
Third pick, San 

Isidera. 


458 gms. 

(lib.) 

...do 

...do.... 


2,438 
2,855 
3,678 


2,282 
2,3S8 
1,753 


252.65 
244. 3S 
180.20 


0. 1107 
.1023 
.1027 


156 

467 

1,925 


8.80 
34.40 
125.30 


0.0561 

. 0736 
.0651 


0.0546 

.0287 
.0376 


158. 12 

159.5 

141.5 


34.5 
34.8 
31 



Table XIII shows there was a smaller number of seeds in the 
sample from the first pick but that the individual seeds were heavier 
and the percentage of lint in the two samples was practically the same. 



PINK BOLLWORM OF COTTOIST IN MEXICO. 



29 



The damaged seed from the first pick weighed less per seed than from 
the second ]^ick, and the damage per seed from the first pick was 
greater than in the second pick. This is probably because the bolls 
from the first pick were attacked when they were greener and the 
seeds were attacked when they were more immature than in the 
other picks. There is no indication that the number of seeds per 
boll is reduced on account of pink bollworm attack, as pointed out by 
Gough. I^nfortunately, the sample of the third pick is from a dif- 
ferent plantation and is not quite comparable with the other samples. 
It may be pointed out, however, that the average weight of the sound 
seed in the second and third picks is almost the same and that the 
loss in the individual attacked seed is greater in the third than in the 
second pick. This is thought to be because a much larger number of 
larva? had prepared to hibo^-nate in the third pick and a hibernating 
larva needs all the available space, especially in the single seed, 
and had eaten out the kernels of the seed cleaner to prepare this space. 
From the data given in Table XIII the loss in weight of the seed in 
the different picks can be calculated, and this is sunmiariz(>d in Tal)le 
XIV. 

Table XIV. — Summdry of table showing the loss in weight nf the seed from the different 
picks due to jnnk bollworm attack. 



Pick. 


Actual 
weight 
of seed 
(grams). 


Loss ill 
weight 
of in- 
fested 
seed 
(grams). 


Corrected 
weight 
of seed 

(grams). 


Per cent 

of loss in 

infested 

seed. 


Per cent 

of total 

.seed lost. 


Remarks. 


First 


261.45 S.42 
278. 78 13. 40 
305. .50 72. 3S 


2(59.88 
292. 18 
377.88 


3.1 
4.(1 
19.1 


1.24 

1.84 

3.82 


First pick=40 per cent crop. 


Second. 


Second pick=40 per cent crop. 


Third 


Tliird !)ick=20 per cent crop. 






Total 








6.90 






i 









Table XIV shows a loss of 3.1 per cent in the weight of the seed 
from the first pick, 4.6 per cent of the second pick, and 19.1 per cent 
in the third pick. The data secured in 1919 showed that 40 per cent 
of the crop was harvested in the first pick, 40 per cent in the second, 
and 20 per cent in the third. The losses in the seed from the dif- 
ferent picks when given their proportionate weights with respect to 
the proportion of the total crop harvested in each pick show that 
1.24 per cent of the total seed was lost in the first pick, 1.84 per cent 
in the second pick, 3.82 per cent in the third pick, or that a total of 
6.90 per cent by weight of the seed is lost due to the attacks of the 
pink bollworm in the pickable cotton. 

When the above-mentioned field samples of seed cotton were 
ginned the seed of the first, second, and third picks were placed in 
separate piles. Using a 20-liter measm-e, an ecjual number of weigh- 



30 



BULLETIN 918, U. S. DEPARTMENT OF AGRICULTURE. 



ings were made of the seed from each pick to determine the loss in 
weight between the seed of the different picks (Table XV). 

Table XV. — Weight of even number of containers of cotton seed for each pick. 



Sample No. 



First 


Second 


Third 


pick. 


pick. 


pick. 


Kilos. 


Kilos. 


Kilos. 


10.5 


10.5 


10.5 


U.O 


10.7 


10. (i 


11.1 


10. G 


10.6 


11.3 


U.O 


10.5 


11.1 


10.9 


10.0 


11.2 


10.8 


10.8 


11.2 


10.9 


10.8 



Sample No. 



Total . 

Average 

Net weight. 



First 
pick. 



Kilos. 
11.1 
10.9 
U.O 



110.4 
11.04 
0.24 



Second 
pick. 



Kilos. 
10.7 
10.9 
10. 5 



107.5 
10.75 
5.95 



Third 
pick. 



Kilos. 
10.7 
10.5 
10.6 



106.2 
10.62 
5.82 



Weight of container, 4.s kUos: container used=20 liters. 

From Table XIV it is shown that there is 3.1 per cent loss in weight 
in the seed from the first pick; therefore the weight of one 20-liter 
measure (6.24 kilos) would be equal to only 96.9 per cent of the weight 
of sound seed, and the corrected weight of a 20-liter measure of sound 
seed should be 6.43 kilos. 

From these data it is shown that there is a loss of 0.19 kilo in the 
seed of the first pick, 0.48 kilo in the second pick, and 0.61 kilo in 
the third pick. These losses reduced to a percentage basis would 
equal 2.9 per cent of the seed lost in the first pick, 7.4 per centin.the 
second pick, and 9.4 ])er cent of the third. But as 40 per cent of the 
crop was harvested in the first pick, 40 per cent in the second pick, 
and 20 j^er cent in the third pick, these figures when given their 
weighted values will equal 5.96 per cent of the total seed lost due to 
pink-bollworm attack. 

This difference of 0.94 per cent between the figures representing 

the total loss in the seed when hand-ginned and when commercially 

gimaed is explained by the fact that part of the damaged seed is 

broken in cleaning and ginning the cotton, and passes out with the 

cleanings, trash, and even in the lint. It is thought, therefore, tliat 

the figure given for the hand-ginned sample, 6.9 per cent, represents 

more nearly the actual loss in the seed of the pickable cotton than does 

the figure 5.96 per cent obtained from the commercially ginned 

sample. 

Loss IN Quantity and Quality of Oil. 

Besides the losses in the weight of the seed, there is also an addi- 
tional loss in quantity and quality of the oil ]:!roduced. 

Because of the danger of introducing the pink boUworm into the 
United States, it was thought advisable not to bring seed out of 
Mexico for analysis. Samples were taken from the different field 
samples as ginned and given to the chemists of the largest oil mill in 
the Laguna district. Owing to the unsettled conditions jDrevailing 
in that section of Mexico during 1920, reports on these samples have 
not been received. 



PINK BOLLWORM OF COTTON IN MEXICO. 



31 



Willcox (7) states tluit there is marked reduction in the quantity 
of oil produced and that the quahty is of an inferior grade. 

NONPICKABLE COTTON. 

It is in this chiss that the major portion of the gross damage 
occurs. As has been previously stated, there is a certain percentage of 
the cotton damaged to such an extent as to render it unfit for picking. 
This cotton naturally is left on the plants after the pickings are 
finished. 

An effort has been made to determine the exact portion of the crop 
that is affected in this manner. By selecting what appeared to be 
average-sized plants (according to the numb(u- of bolls per plant, 
etc.) in fields of several different average plantations, about 3,000 
plants were examined after the cotton had been picked. These 
plants were examined individually, the total number of bolls on 
each plant and total number of bolls lost on each plant due to attack 
of the pink bollworm being recorded. In counting the total numl)er 
of bolls an empty burr was counted as a boll, and in the calculations 
has the weight of a perfectly sound boll. 

In counting "bolls lost," only bolls or portions of bolls which 
showed plainly that their damage was caused by the pink bollworm were 
taken into consideration. Bolls or portions of bolls that showed 
themselves to be unfit for picking because of conditions other than 
the pink bollworm, such as those attacked by the comrhon bollworm, 
C. ohsoleta, or injured by water, heat, and drvness, were counted as 
sound bolls (Table XVI). 



Table XVI. — Loss to crop in nonpichable cotton caused h>/ the pink bolliconn. 



Place. 



Total 
plants. 



Total bolls. '^''1^^^^^°'^' 



Percent 
damaged 



Honniguero. 

Alvia 

LaConcha. . 
Sanlsldera. . 

Zaragosa 

Rosas 

Barcelona... 



Total . . . 

Average. 



24S 
453 
503 
4.54 
4.50 
450 
300 



0,737 
14,977 
1.5,117 
20,112 
10,42S 
9, 2S2 
6, 297 



.S2,9.50 



1,066 
2,61,S 
2,942 
3,76S 
2, .544 
2,318 
1,325 



16,581 



15.82 
17.48 
19. 46 
18. 73 
24.39 
24.97 
21.04 



141.89 
19.98 



Table XVI shows that of 82,950 bolls produced by 2,858 plants 
16,581 were lost, making a total of 19.98 per cent damage in the non- 
pickable cotton due directl}- to the attack of the pink bollworm. 
The plantations on which these figures are based represent a true 
average of the entire Laguna. In addition to these plantations, a 
number of other places were visited in different parts of the Laguna 
and the amount of damage found ranged from 15 to 25 per cent, with 
an average of approximately 20 per cent loss due to the pink ])ollworm, 
which substantiates the accuracy of the foregoing estimates. 



32 BULLETIN 918, IT. S. DEPARTMENT OF AGRICULTURE. 

SUMMARY OF DAMAGE BY THE PINK BOLLWORM.< 

(1) Loss in squares and blooms: 26. S per cent of the squares and 

blooms shed. 

(2) Loss in pickable cotton: 

Lint: Deterioration in quality. 

Seed: Is reduced 6.9 per cent in weight; quantity and 
quality of oil also reduc-ed. 

(3) Loss in nonpickable cotton: 19. 9S per cent of entire crop ren- 

dered un])ickable. 

The damage to the nonpickable cotton and the loss by weight in 
the seed in the pickable cotton can be reduced to a monetary basis. 
Assuming lint to be worth 30 cents per pound and seed worth $60 
per ton, the value of 500 pounds of lint would be $150 and 1,000 
pounds or h ton of seed would be worth $30, or a total of $180 per 
bale. For every bale picked there is 19.98 per cent of the seed and 
lint left in the field as nonpickable cotton, or, in other words, the 
amount of cotton actually picked represents only 80.02 per cent of 
the crop if no pink bollworms were present. Then the value of the 
crop produced would be $224.90 rather than $180. The loss of 
19.98 per cent of tlie potential crop ($224.90) is equal to $44.93 per 
bale. In addition to this there is 6.9 per cent loss by weight in the 
seed of the pickable cotton (which represents the 80.02 per cent of 
the bale not included in the 19.98 per cent loss or nonpickable cotton), 
which amounts to $2.07. Therefore the total loss is $47 or 20.89 
per cent of the value of the bale. 

The calculable loss that can be specifically stated on a definite 
percentage basis is 20.89 per cent. In addition to this figure there 
should be added the losses incurred in the shedding of the squares, 
deterioration in the quantity and quality of the oil in the seed, and 
the weakening and irregularity of the staple in computing the total 
damage caused by the pink bollworm. 

FOOD PLANTS. 

While cotton (Gossypium, spp.) is by far the most favored food 
plant, a number of other plants have been recorded as host plants of 
the pink l)ollworm. Maxwell-Lefroy (2) records a species of Hibiscus 
and the oily seed of trees (species not given) in India; Fullaway (3) 
reared a single specimen from milo {Thespesia populnea) in Hawaii; 

* Damage during 19-20. — The damage to the Lagiuia crop by the pink bollworm was luiusiially severe 
during 1920. Frost did not come in 1919 till very late and this was followed by a mild winter, which 
allowed a large percentage of the hibernating larvp to pass the winter successfully. The fields were ex- 
amined during the latter part of June, and it was very evident that the infestation in squares and young 
bolls was heavier than it had been in 191S or 1919. The cotton was also further advanced and was growing 
rapidly, with very good prospects for a large crop. About this time there were severe outbreaks of 
aphids {Aphis gossypii), thrips, and rust {Accidium jossypii) which checked the growth of the plants 
and gave them a setback from which they never recovered. This caused the plants to produce very few 
bolls, and the infestation by the jiink bollworms and the percentage of loss have consequently been very 
high. Estimates made in November showed that the pink bollworm had injured 31.3 per cent of the 
crop so badly that it was rendered inifit for picking and that there was 7 or S per cent additional loss 
attributalile to the insect by the lowering of the quantity and quaJity of the pickable cotton, or a total of 
38 to 39 per cent loss of the crop. 



3ul. 918, U. S. Dept. of Agriculture 



PLATE IV. 




PINK BOLLWORM. 

Larvie feeding iu the walls of the puds aud seed of okra. 



PINK BOLLWOEM OF COTTON Ilf MEXICO. 



33 



Busck (8) hrod tlio pink l)ollworm from Gosfiypinni tomentosvni in 
Hawaii, but did not find it in mik>; King (.9) reports it from hanbuk 
(Ahutilon sp.) in Africa; and Gough (12) records mallow {Malva sp.). 
Willcocks (7) states that the food plants in Egypt are bamia or okra 
(Hihiscus esculcntus), teel or hemp (Ilihiscus cannahinus), and holly- 
hock {Aliliaea rosea). 

A number of malvaceous plants were grown ])eside heavily infested 
cotton on the lal^oratory grounds and several became infested. 
Okra (IliJmcus esculentus) became rather heavily infested in every 
instance when grown in close proximity to cotton. Table XVII 
is a complete record of all the seed pods grown on 80 plants at 
the laboratory during the season of 1919. From August 14 to 
December 8, 590 seed pods were examined with the following results: 
66.7 per cent were infested with live larvae and pupa?, and the total 
infestation, including seed pods that were unmistakably infested but 
in which no larvjp or pupa? were found, was 78.8 per cent. The in- 
fested seed pods averaged 2 larva\ pupa", and exit holes. 

Table XVII. — Seed-pod examination of Okra {11. esmlentus). 



Num- 
ber of 
pods. 


Pods infested. 


Infestation. 


Num- 
ber of 

infe.sted 
pods 

without 
larvae 

or 
pupae 

pre.sent. 


Num- 
ber of 
exit 
holes. 


Remarks. 


Num- 
ber. 


Per 

cent. 


LarviB 
total. 


Num- 
ber of 
pupa'. 


Pupae 

and 

larvae. 


3S 
33 

M) 
101) 
11 H) 

84 
20 
20 
35 


11 
9 
3(1 
35 
69 
79 
45 
66 
12 
17 
15 


2S.9 
27.2 
60.0 
70.0 
69.0 
79.0 
90.0 
78.5 
60.0 
85.0 
42.8 


9 
9 

48 
85 
105 
106 
92 
147 
37 
35 
21 



n 



5 
4 
5 





9 
9 
4S 
85 
105 
111 
96 
152 
37 
35 
21 


3 
1 

1 
3 
13 
13 
2 
5 
1 
1 





• 





25 

37 

13 

8 



1 




Green pods. 

Do. 

Do. 

Do. 

Do. 

Do. 
Dry ]iods. 

Do. 

Do. 

Do. 
Green pods. 


590 


394 1 60.7 

1 


694 


14 


708 


43 


84 





Fi'om this one observation it seems that when attacking okra the 
pink bollworm is more inclined to pupate in the seed pods than in 
the bolls when cotton is attacked. No plausible explanation can be 
given as to why this should occur. 

The manner of attack and feeding habits in okra are essentially 
the same as in cotton, but no larvae were ever foimd feeding in the 
flower buds or flowers. 

Double seeds or three or four seeds are frequently webbed together 
in much the same manner as double seed in cotton, though the work 
is not so clean and particles of frass are usually found attached to 
them. Plate IV shows full-grown larvae feeding in okra pods. 

One important point to be determined is whether the species is able 
to sustain and perpetuate itself on okra alone as a food plant. Two 



34 BULLETIN 918, U. S. DEPARTMENT OF AGRICULTURE. 

large screen cages were constructed over heavily infested okra in the 
fall of 1918. The entire plants with the fruits attached were left in 
the cages during the summer of 1919. Repeated examainations were 
made of all fruits formed during 1919 and no infestation ever devel- 
oped from the hibernating larvte. The protection afforded by the 
okra is not as good as the protection afforded by cotton. The seed 
pods crack open on drying and the seeds with the larvse webbed up 
in them drop to the ground, the larvoB becoming subject to the detri- 
mental effects of water and attacks of insect enemies. 

Under the same conditions hollyhock (Althaea rosea), a very com- 
mon ornamental flower, was found to be subject to the attack of the 
pink boUworm larvse, the insects being found in the buds, flowers, 
and seed pods. 

IIil)ernating cages were also constructed over hollyhock plants 
and experiments conducted in the same manner as with okra with 
negative results. No reinf estation occuiTed from hibernating larvae. 

The flower buds, flowers, and seed pods of Ilihiscus syriacus were 
attacked by the pink bollworm, the manner of attack and feeding 
habits being the same as in cotton and okra. The inf(^station in the 
flower buds was light, but the seed pods were nearly all infested and 
some contained several larvae. 

One pink bollworm larva was taken from a seed pod of the Con- 
federate rose (Hibiscus mutahilis). 

Seeds from 25 species of malvaceous plants were collected in 
southern Texas and planted in close proximity to cotton at Ciudad 
Lerdo. Of this number only the following species grew : Ilihiscus cocci- 
neus Walt., Hibiscus militaris Cav., Hibiscus lasiocarpus Cav., Mal- 
vastrum americanum (L.) Terr., Sida spinosa L., Wissadula lozani 
(Rose) Fries, and Kosteletzh/a virginica L. Some of these have small 
seed pods and are not well adapted to the feeding habits of the larva?, 
but the following species were attacked by pink boUworms. 

Only one plant of Hibiscus coccineus grew. It developed 7 seed- 
pods and 5 of these were infested. 

Hibiscus militaris was attacked both in the flowers and seed pods. 
The same rosette appearance takes place in the infested flower as in 
upland cotton. 

Kosteletzhya virginica was also attacked. The plant is a very pro- 
fuse bloomer, but the seed pods are rather small to be well adapted 
for the larvae, though two full-grown larvae were found in seed pods. 

Malvastrum americanum was infested. One specimen was taken 
in a seed pod. 

A species of Malva ( Malva jyarvi flora L. ?) grows rather abundantly 
along the borders of the fields in the Laguna, but was never found 
to be infested under natural conditions. The seed pods are too small 
to be well ada]:>ted for pink bollworms, though larvae can reach ma- 
turity in a single pod. 



PINK BOLLWOEM OF COTTON IN MEXICO. 35 

DISPERSAL. 

The most important factor in the dispersal of the species is man. 
By his transportation of cotton seed and cotton products he has car- 
ried the insect from its original home to all parts of the cotton-produc- 
ing world. Once it is established, local dispersal from one field to 
another is also by flight, and in some instances the carriage of the 
larvae by water is of importance. 

CARRIAGE OF LARV^ IN SEED FOR PLANTING AND OTHER PURPOSES. 

The transportation of infested seed ])y man from place to place is 
the usual means by which this insect is carried to new localities. It 
was introduced into Mexico in *1911 with seed for planting; into 
Brazil in 1911-1913 with seed for planting; and more recently into 
certain parts of Texas with seed in cotton and seed for milling pur- 
poses. From what has already been stated concerning the habits 
of the pink bollworm, it is evident that seed from an infested field is 
sure to contain a certain percentage of infestation, and it is known 
that the resting larvcie can live for at least 2 years in such seed. It is 
thus seen that the larvse are admirably adapted for transportation 
over great distances in this way. Seed, moreover, is often inci- 
dentally carried with other products, llailroad cars which have 
been used for shipping cotton seed are a very dangerous example of 
this. Seed will usually be found in the cracks and corners and be- 
tween the walls of the car. Numerous instances of this have been 
noted, particularly by inspectors at border points, where live pink- 
bollworm larvae were taken from cars which had been used for seed in 
the Laguna district and later used for exportation of other products. 
Bales of cotton often carry seed and as many as several hundred seeds 
have been found mixed with the lint and attached to the bagging. 
Cotton waste and used cotton bagging are other items usually having 
seed attached to them. Cotton pickers in Mexico often move from 
plantation to plantation. It is a common practice with them to carry 
their own picking sacks and among their belongings seed cotton and 
cotton seed are often found. These and similar practices are common 
means by which the insect is carried. 

FLIGHT AND CARRIAGE OF ADULTS. 

While the moth of the pink bollworm is small, it has ample wing 
power for its size and is capable of quick, darting flight. When 
disturbed during the day it flies only a short distance and hides 
under the nearest object. On the other hand, several hundred 
moths were liberated on top of the house where a light breeze was 
blowing, in the morning and at dusk. About half of those liberated 
in the morning flew only a few feet before settling down, while the 
others flew upward and away as far as the eye could follow them. 
Those liberated at dusk nearly all flew upward and away till lost to 
sight. In all cases they flew with the wind and not quartering to it, 
as some insects do. Up to the present time no conclusive data have 



36 BULLETIN 918, U. S. DEPARTMENT OF AGRICULTURE. 

been accumulated along this lino, due to the nocturnal habits of the 
moth and the fact that in Mexico it was so generally distributed that 
no uninfested isolated fields were found. 

The average duration of the moth stage in captivity is about 14 
days. If the moth flies only a short distance before coming to a rest, 
it would appear certain that it may again proceed for another short 
distance. If there were nothing to influence the direction of its 
flight, it might fly in any direction and as likely as not return to its 
original starting point; but if the direction of the flight is influenced 
by the wind, as it was in our observations, it would fly with the wind, 
and where there is a prevailing wind from one direction the moth 
would be carried in the same general direction farther and farther 
from its starting point and might cover a considerable distance 
before dying. In the eradication work in Texas a 5-mile non- 
cotton zone around infested territory is used to prevent dispersal 
by flight, and it is thought this zone is reasonably safe. The moths 
have seclusive habits, and frequently hide in cracks, crevices, and 
dark corners. At the railroad stations in the Laguna cars stand 
upon the side tracks within a few yards of the cotton fields for days 
or even weeks at a time while being loaded and unloaded. Trains stop 
for long periods of time near the fields to unload supplies, and when 
these stops are made at night, when the moths are flying about, it is 
possible that some of the moths might secrete themselves in the cars 
and later be carried to distant points. There is the same danger, though 
to a lesser degree, in vehicles passing cotton fields along the roads. 

CARRIAGE OF LARV^ BY WATER. 

Cotton plants with bolls attached were often seen floating down 
the Rio Nazas when it was at flood stage, and old bolls are carried long 
distances when fields are overflowed. Some experiments were made 
at Dr. W. D. Hunter's suggestion to determine how long larvae could 
survive exposure to water. Free larvae with no protection whatever 
pupated and produced moths after being in water in tubes for 44 hours. 
Larvae survived for several days after being in water longer, but 
none produced moths. Larvae in cocoons survived 72 hours in water 
in tubes and free larvae placed in pill boxes perforated with a needle 
produced one adult after 8 days' submergence in a pitcher. Pupae 
did not survive as long as larvae. Old bolls picked in January, 1918, 
and stored in the laboratory till April, 1919, were sul)merged in 
water and left floating on the surface of water in a trough. Larvae 
pupated and produced adults after 7 days in both instances, but no 
adults emerged after 11 days in either case. 

Several plants containing green bolls heavily infested were placed 
in the river and tied so that they could not float away. When there 
was enough current in the river to keep the plants floating at the 
end of the string the bolls were all washed away at the end of 4 to 5 
days. When there w^as no current the plants sank to the bottom 
and all the larvae were found dead in 3 days. It is quite likely, however, 



PINK BOLLWORM OF COTTON IN MEXICO. 



37 



that when phmts are allowed to float free and move with the current 
the bolls will remain on the plants longer. When floating in this 
manner part of the plants are always out of water and, as tliey revolve 
more or less, the same bolls will not be submerged all the time and 
larvae will survive more than 3 days. To determine how long larvse 
would live in green bolls, sample bolls were ])laced in a trough 
and examined daily. The bolls floated and larva^ lived for 10 days. 
On the eleventh day all of the bolls sank to the bottom and were very 
rotten, and no live larvse were found in them. The results of these 
experiments are summarized in Table XVIII. 

Table XVIII. — Effect of water on pirtl: hoUuorm lamr. 



Condition of exposure. 


Number treated. 


Time of 
expo.sure. 


Per cent 
killed. 


Remarks. 






Hour'! 






Loo.se liirvio in tiil>e of wat.er. .. 


.') larvfc 


20 


00 


1 pupated afterwards. 

2 pupated afterwards. 




Tlarva^ 


44 


70 




20 larva- ami :'. iiu|);r. . 


120 


100 


Larvae lived several flays. 




:«) larva' 


144 

48 


100 

70 




Loose cocoons in tube of water. . 


lOlarviE 


Heavy cocoons: I adult 










emerged. 




20 larva? 


72 


90 


Heavv cocoons. 




do 


9li 
120 
90 


100 
100 
100 


Do. 




iniarvic 


Do. 


Double seed in tubi^ ofwater... 


10 double seed (r, lar- 






va'.) 
10 double seed Ci lar- 


124 


00 


2 larvre alive. 


Seed nnd cocoons in pill 1")oxes 


v.e.) 
1 1)0X 


24 
4S 
72 
90 






40 






perforated with needle 


do 




(3 seeds and 2 cocoons in each 
bo.x. Counted together). 


....do 




do 






do 


120 

Da lit;. 


50 


2 pupated afterwards. 




do 


■(■,.5 


40 






do 


s 


00 






do 


11 


100 






do 


15 
17 

7 


100 
100 

80 






21 l)oxes 




Rolls floatinu on water in 


20 bolls (29 larva') 


Bolls covered with algse 


trough, (liolls picked in 








and rotten. 


December, 191.S, and stored in 


20 1)olLs(121arva-) 


11 


100 


Do. 


laboratory. Contained many 


20 lioUs (.'■)() larvic) 


14 


100 


Do. 


dead larvic not included in 


20 1)olls(171arva') 


17 


100 


1)0. 


coimt.) 


120 bolls (273 larva')... 


18 


100 


Do. 


Bolls submerged in water in 


20 bolls (30 larva-) 


7 


77 


2 i)Upated; boUs^ covered 


trough (same kind of bolls as 








with alga' and rotten. 


above). 


20 bolls (113 larva').... 


11 


100 


1 larva lived several days; 
bolls rotten. 




20 l)0lls{4(i larva') 


14 


100 


Bolls rotten. 




20 1)olls(14!arv;r) 


17 


100 


Do. 




120 liolls (109 larva')... 


18 
Ihrnn. 


100 


Do. 


Green bolls submerged in slat- 


10 bolls (37 1arv;c) 


48 


95 


Bolls fermenting and very 


ted box in river. 








sticky. 




lObolls 


72 
90 

48 


100 
100 


Interior liolls rotten. 




10 bolls 


Badly rotted. 


Plant with green liolls attached 


10bolls(401arva^) 


Bolls fermenting. 


floating on surface of river, 


9 1)olls(191arva') 


72 


98.4 


Interior of liolls rotting. 


Sept. 13, 1919. 


7 bolls (11 larva:') 


91, 
Dat/f. 


40 


All of live larva' found in 
two bolls which were not 
submerged. 


143 green cotton bolls placed in 


20 bolls (122 larva').... 


3 


7.3 




container of water. Water 


20 bolls (125 larva').... 


4 


3.1 


All dead in two badly de- 


changed daily. 








cayed bolls. 




20 bolls (133 larvre).... 


5 


0.3 


Decaying. 




20 bolls (107 larva-).... 





00.7 


Some in bad state of decay. 




1.5 bolls (K4larv;t') 


7 


31.5 


Do. 




l(i bolls (73 larva') 


8 


38. 8 


Some bolls rather small 
and badly decayed. 




10 bolls (01 larva') 


!t 


44.2 


Bolls decaying rapidly. 




10 bolls (51 larva') 


10 


00.7 


Some still" floating; badly 
decayed. 




6 bolls (43 larva_-) 


11 


100.0 


Badly decayed. 




G bolls (29 larva') 


12 


100.0 


Very rotten. 



38 BULLETIN niS, U. S. DEPARTMENT OF AGPJClULTURE. 

In general, it may be said that larvae will live in bolls submerged 
in water or floating on the siu'face of the water till the bolls them- 
selves are thoroughly rotten. This may be a week or more, depend- 
ing upon the condition of the bolls. The old dried bolls and larvae 
webbed up in bits of rubbish are particularly likely to carry an infes- 
tation a long distance, for they float more readily than green bolls. 
One of the large plantations was considering dividing their property 
into zones which would be planted in cotton only every third or 
fourth year in order to reduce the damage by the pink bollworm, but 
the danger of reinfestation by irrigation water was considered so great 
that it was not adopted. 

NATURAL CONTROL. 

From the data collected in 191S and 1919, it is concluded that the 
maximum infestation and the maxim.um damage to the cotton of 
the Laguna have been reached l)y this time, except for slight yearly 
variations due to climatic conditions which may have some efl^ect 
on the development of the pink bollworm and its attack on the 
cotton. It is the belief of the plantation owners that the damage 
or loss to the crop has remained al)0ut the same since 1916, or that 
the maximum had been reached at the end of five years from the time 
of introduction. 

MORTALITY OF NEWLY-HATCHED LARV^. 

It has been shown in Table III that 47.1 per cent of the pink 
bollworm eggs are not deposited on the squares or bolls. The larvae 
from these eggs must crawl some distance before reaching food. In 
this migration they are readily attacked by insect enemies, are ex- 
posed to the hot sun, become weakened and exhausted, and event- 
ually may succumb to starvation. It is thought that very few or 
possibly none of the larvae from this 47.1 per cent of the eggs ever 
enter the squares or bolls. Many of the larvae from the remaining 
52.9 per cent of the eggs deposited on suitable parts of the plant 
never succeed in entering the bolls or squares either. To determine 
what percentage of the larvae hatching from eggs deposited on the 
plants fail to enter the bolls or squares, five plants were examined. 
These records were carefully made. Every part of the plant was 
closely examined with a hand lens for eggs and eggshells. The larvae, 
pupae, and exit holes were also carefully counted and the mortality 
rate calculated from the number of eggshells found on the plants 
and the total infestation of the plants. The results are given in 
Table XIX. 



PINK BOLLWORM OF COTTON IN MFAKX). 
Table XIX. — Mortality of larva of P . (jossypiella. 



39 



Num- 
ber of 
plants. 


On plant. 


Number of 
larvEO. 


Pupffi 
found. 


Exit 
holes. 


I>arvfp, 
pupa>, 

and 

exit 
holes. 


Per 

cent 
mor- 
tality. 


Remarks. 


Num- 
ber of 
shells. 


Num- 
ber of 

eggs. 


Iff 

squares. 


In 
bolls. 




181 
141 
190 
170 
10.3 


89 
111 
115 

53 
143 


3 
1 
6 

2 


17 

46 
84 
25 
39 





3 



7 
12 
24 
13 
15 


27 
59 
114 
41 

57 


85.1 
58. 2 
40.0 
75.9 
44.7 


10 bolls on plant. 
2S bolls on plant. 


5 


785' 


511 


12 


211 


3 


72 


298 


62.1 



From this table it is seen that the mortality varies from 40 to 85.1 
per cent with an average of 62.1 per cent. If it is assumed that 
none of the larvae from the 47.1 per cent of tlie eggs laid on other 
parts of the plants ever succeed in entering the l)olls or squares, this 
would still leave 15 per cent of the larva? from eggs laid on the squares 
and bolls unaccounted for. Since many eggshells had undoubtedly 
fallen from the plants examined, this percentage of mortality (62.1 
per cent) is smaller than what actually occurs. 

To determine what percentage of the eggs laid on the bolls are 
lost, 16 samples of 25 green bolls each were examined, the number of 
eggs laid on them counted, and the total infestation found (Table 
XX). 

Table XX. — Mortality of pink holhvorm law »' from ec/gs laid on bolls. 





Eggs. 


Larva?. 


Exit 
holes. 


Pupse. 


Total 
infes- 
tation. 


Per cent 
of larvse 


Number of bolls. 


Tip. 


Base. 


Total. 


First. 


Second . 


Third. 


Fourth. 


from 
eggs laid 
on bolls 
recovered 
in bolls. 


400 


61 
0.15 


4,958 
12.4 


5,019 
12.5 


190 

0.47 


347 

0.S7 


442 
1.1 


1,005 
2.5 


386 
0. !IG 


1 


2,371 
5.92 


45 8 


Average 









There were 5,019 eggs and eggshells on the bolls. If larvae from 
all these eggs had hatched and all tlie larva^ gone into the bolls, there 
would have been an average infestation of 12.5 larvae per boll, whereas 
an average of a little less than 6 larva? was actually found. These 
examinations were made in October and later examinations showed 
that the maximum infestation ever reached was an average of 7 per 
boll. 

These figures indicate that about half of the lai'va? from eggs laid 
on the bolls themselves never succeed in entering them. In Table 
III it was shown that 51.7 per cent of the eggs were laid on the bolls 
and appendages, and if only half of these successfully enter the bolls 
this would be equal to 25.8 per cent of the total eggs. This loss of 



40 BULLETIN 918, U. S. DEPARTMENT OF AGRICULTURE. 

25 per cent, in addition to the 47.1 per cent laid on other parts of 
the plants and assumed to be lost, would bring the total mortality 
of young larvcB up to 72.9 per cent. This figure (72.9 per cent) is 
thought to approach more closely what actually takes place in the field 
than that of 62.1 per cent based on the number of empty shells found. 
This is borne out by laboratory experience where the mortality was 
90 per cent or more. 

Once the larvne are inside the bolls there is very little or no mor- 
tahty during the summer months. 

MORTALITY OF HIBERNATING LARV^ IN THE FIELDS. 

There is a very heavy mortality in hibernating larvae left in the 
fields during the winter, especially when the fields are irrigated. Ex- 
aminations of old bolls picked up in the fields showed that about 80 to 
90 per cent of the larvte survived till February, and that the mor- 
tality rapidly increased from this date onward. The mortality varies 
greatly in diff'erent samples, but by the end of March it is difficult to 
find any live larvae in the scraps picked up on the ground in the fields. 
There are still live larvae present, but the old bolls have broken up, 
scattered, and in cultivated fields are difficult to find. On March 
13, 1918, only 3 live larvae were found from a ])ushel of old bolls and 
trash picked up in a lightly infested field at San Pedro. On April 
16, 1919, no live larvae were found in the old bolls left on the ground 
after cattle had grazed over the fields at Tlahualilo, but about 5 per 
cent were still alive in the bolls left on the stalks. 

To secure more data on this point, two series of experiments were 
started on November 26, 1918. One experiment was under as nearly 
normal irrigated field conditions as possible and the other under non- 
irrigated conditions. The fields in the Laguna are usually irrigated 
in November, December, or January, when (u)tton follows cotton, as 
it does on most plantations. When fields have been lying fallow for 
a season, the water is applied any time during the year when it is 
available. About 3 feet of water is placed on the fields and allowed 
to soak in. This requires from one to several months, depending 
upon the character of the soil. In the experimental plot irrigation 
was started on December 2 and continued till December 8, when the 
motor burned out. Water was again applied on December 23, 1918, 
and continued daily until January 22, 1919. On account of the 
small amount of electric current available, the plot could not be filled 
3 feet deep, but the daily application of a few inches of water kept 
the ground thoroughly wet and covered with water at least part of 
each day. 

In each of the series the lai'Vge were exposed under wire cages in 
bolls in a single layer on the surface of the ground, iii bolls buried 6 
to 7 inches deep, and in double seed bui'ied one-fourth inch deep in 
flowerpots which were set in the soil liush with the surface. More- 



PINK BOLLWORM OF COTTON IN MEXICO. 



41 



over, larvge removed from all seed and lint were placed in screened 
boxes and flowerpots and allowed to enter the soil. These were also 
buried flush with the surface of the ground. A sample of the l)olls 
used was examined at the time and found to contain an average of 
6.64 fourth-instar and 0.03 thu'd-instar larvae per boll. The material 
was examined at different dates and the results are given in Table XXI. 

Table XXI.- — The mortality arnnnc/ hibernating Pectinophora t/ossypiella larinv under 

different field conditions. 



Ex- 


Conditions of exposure. 


Examination. 




ment 

No. 


Date. 


Live 
larvae. 


Dead 
larvae. 


Live 
pupae. 


Pupal 
skins. 


Remarks. 


557 


300 larvae removed 
from seed and lint 
and buried in wood- 
en box of soil in 
irrigated plot. 

50 larvae in flowerpot, 
same as 557. 


1919. 
June 11. 

May 10.. 












12 

28 


6 





39 
20 
74 
51 

52 
13 


68 

54 

83 

152 






2 

Several. 

3 












3 

1 


1 







1 

2 
6 


2 





2 












2 

1 


3 





10 

3 
2 

IS 


10 




6 
11 

7 



61 empty dirt cells 


558a 




around side of box. 


558c 


June 10 




558b 








558D 


50 double seed.s buried 
in flowerpot on irri- 
gated plot. 

300 larvae removed 
from seed and lint 
and buried in wooden 
box of soil in nonirri- 
gated plot. 

50 larvae in flowerpot, 
same as 560. 


June 11 


Seed well rotted. 


560 


June 12 


I^arva" webbed up on 


561a 


May 10 


1 

7 


side of box. 
Larvw in cocoons. 


561b 


June 11 




561c 


50 double seeds in flow- 
erpot on nonirrigated 
plot. 

200 green and dry bolls 
buried 6 to 7 inches 
deep on irrigated 
plot. 

200 green and dry bolls 
left on top of ground 
on irrigated plot. 

200 green and dry bolls 
buried in soil 6 to 7 
inches deep on non- 
irrigated plot. 

200 green and dry bolls 
lefloiilopofgroimd 
on uouirrigated plot. 


June 12 


Seed well rotted. 


559a 


Mar. 10 

bolls). 
Apr. 24 

bolls). 
May 16 

bolls). 
June 6 

bolls^. 
Mar. 10 

bolls). 
Apr. 24 

bolls). 
May 15 

bolls). 
June 4 

bolls). 

Mar. 11 
bolls). 

Apr. 24 
bolls). 

June 7 
bolls). 

Mar. 11 

bolls). 
Apr. 24 

bolls). 
May 15 

bolls). 
June 7 

bolls). 
July 25 

bolls). 
Aug. 22 

bolls). 


(10 
(10 
(50 

(130 
(10 
(10 
(50 

(116 

(10 
(10 
(180 

(10 
(10 
(50 
(50 
(25 
(SO 


65 
48 


Boll.s rotting badly. 

Very rotten and fallen 

to" pieces. 
Fallen to pieces. 






Bolls so rotten dithcult 


559b 

562a 
562b 


29 
36 
194 
344 


13 


26 
28 
137 

188 

100 




to pick from soil. 
Bolls in good condi- 
tion. 
Do. 

Some of bolls getting 
rotten, but those 
which had opened 
when experiment be- 
gan still in good con- 
dition. 

Bolls badly rotted. 

Badly rotted and could 

not separate bolls. 
Thoroughly rotten. 

Bolls in very good con- 
dition. 
Do. 

Do. 

Do. 

Do. 

Do. 



4:2 BULLETIN 918, U. S. DEPARTMENT OF AGRICULTURE. 

Table XXI shows that no live larvae were found during May and 
June among those removed from seed and lint or in double seed 
buried in the irrigated plots (Experiments Nos. 557 and 558 A to D), 
and that 12.8 per cent were alive or had emerged as moths under the 
same conditions in the nonirrigated plot (Experiments Nos. 560 and 

561 A to C). No live larvae were found in bolls buried in irrigated 
plots from March 10 (the first examination) until June 6 in Experi- 
ment No. 559 A, and none in bolls buried in nonirrigated plot (Experi- 
ment No. 562 A) after April 24. The surrounding soil had been irri- 
gated and when the last examination was made on June 7 the soil in 
the nonirrigated plot was found moist about 3 inches below the surface 
from water that had seeped in from below. From this experiment 
6.2 per cent survived till April 24. There was less mortality in the 
bolls when left on the surface of the ground than when buried. In 
the irrigated plot (Experiment No. 559 B) live larvae were found in 
bolls left on the surface of the ground at the last examination on 
June 4, 1919, and 9.7 per cent had survived or previously emerged 
as moths on this date. On the nonirrigated plot (Experiment No. 

562 B) 50 per cent of the larvae in bolls on the surface were alive on 
June 7, 1919. At the next examination, on July 25, all of the larvae 
were dead. 

In all of the experiments, especially the later examinations, many 
of the larvae were not recovered because the dead larvae were so decom- 
posed they w^ere not recognizable. Very few if any escaped, for the 
buried bolls had close-mesh wire screen over the top and along the 
sides, extending below the level of the bolls. The earth surrounding 
the material was carefully sifted and larvae and pupal skins found 
here counted with the others. The percentages of mortality for the 
bolls are based on the number of larvae found in the samples at the 
beginning of the experiments. This is. not absolutely accurate, 
because the number of larvae may vary considerably in individual 
bolls, but it is the most reliable figure to use inasmuch as the actual 
number of dead larvae could not be determined. 

It is seen that the mortality increases as the season advances, even 
where the conditions were most favorable, no live larvae being found 
as late as July 25, and that the mortality in all the experiments was 
greater when the larvae were buried than when they were left on the 
surface, and greater when the plots were irrigated than when left dry. 
These experiments also show that the greatest danger for starting 
a new infestation from material left in the fields is the old bolls 
left on the surface of the ground. Over 9 per cent of the larvae in 
these bolls on the irrigated plot survived till June 4 and 50 per cent 
survived in the nonirrigated plot. At this season the cotton will be 
large enough for oviposition to begin. Under the usual field condi- 
tions the irrigated lands will have been cultivated before this date 



PINK BOLLWORM OF COTTON TN MEXICO. 43 

and the mortality increased by breaking up and burying the bolls. 
On the other hand, the bolls float on water and the wind frequently 
blows them against the borders on one side of the field, where thev^ are 
piled up several inches or more deep. This concentration keeps some 
of the bolls out of the water and affords more protection for the bolls 
in the interior of the pile against heat and cold. If the fields are not 
irrigated it means they will not be planted the following year and 
such fields are usually grazed by goats, cows, and burros, which eat 
many of the bolls. 

Whether or not the results obtained in these experiments during 
only one winter^ hold true for what actually takes place in the Laguna 
it is impossible to say, but they indicate beneficial results from irriga- 
tion and burying the bolls. That a very heavy mortality, probably 
more than 95 per cent, does take place in the fields is shown by field 
examinations of the bolls and the very light infestation in the early 
part of the season. There are such enormous numbers of larvsB 
liibernating in the fields that the crop would be entirely destroyed 
if the mortality was not very high. 

Willcocks (7) in Egypt left bolls out of doors exposed to the sun on 
the surface of dry ground and ground that was watered periodically 
(three waterings). He found a very high mortality during April, 
May, and June, and all the larvse were dead on June 25. There was 
a slightly higher mortality among the larvne in the watered bolls and 
all the larvae were dead on April 8, while some survived in the dry 
bolls till May 3. His figures ''most certainly show that the chance of 
resting-stage pink bollworms surviving in the bolls fully exposed to the 
sun on the surface of dry sheraki land in Ma}-, June, and July is a re- 
mote one." He buried another lot of bolls on November 24 in damp 
soil in boxes. Some of these were kept dry and others wet. Some 
were stored indoors and others outdoors, though none were in direct 
sunlight. There was less mortality in the buried bolls than in those 
left on the surface exposed to the sun, and he says, in speaking of wet 
conditions, "this does not seem to be materially disadvantageous to 
the pest. " In all of the buried bolls there was a decided emergence 
of thelarvue to the top of the soil, which began as soon as the bolls were 
buried (November 24) and continued intermittently in some cases 
where the bolls were kept dry till the following November. Water 
hastened this larval emergence when applied in the fall or the fol- 
lowing spring, but though the bolls were badly rotted the larvae were 
still able to remain in them, and spun up in their almost water-tight 
cocoons during March, April, and May. 

In our experiments in Mexico, larvae survived better in bolls on 
the top of the gromid than when buried and better when left dry 
than when irrigated. In Mexico the temperature was never as high 

'■These results were substantiated by experiments during the winter of 1919-20. 



44 BULLETIN 918, U. S. DEPARTMENT OF AGRICULTURE. 

as it is in Egypt in May and June (107° and 111° F.) and our bolls 
received some protection from the sun by the screen covering of 
the irrigated bolls and the cheesecloth covering over the nonirri- 
gated bolls. Furthermore, our bolls were probably kept wetter 
during the 30 days when they were wet than Willcocks's were, but 
his were kept wet for a longer time. There was but very little larval 
emergence in any of our boUs. This is shown by the large numbers 
of dead larvie fomid in situ in the earlier examinations, when they 
were still recognizable, and by the few larvae or pupal skins fomid in 
the surrounding soil. There was more larval emergence from the 
bolls in the irrigated plots w^here 12 pupal skins were fomid in the 
soil than in the nonirrigated where only 2 or 3 were found. About 
half of the larvas recovered in the bolls w^ere in the lint, but no count 
was kept of this point and it is not known whether there were more 
than are usually found in lint in the bolls in the fields during the 
fall or not. In the case of the double seeds in the irrigated plot the 
following note was made: "Earthen cells were noticed in a few 
instances, apparently some of the larvae left the seed." In the double 
seed on the nonirrigated plot 4 pupal skins were found in the soil. 

On March 11, 1919, 100 bolls which were picked on December 7, 
1918, and stored in the laboratory till this date were buried 1 to 2 inches 
deep in a box of soil and wet thoroughly. The box was sprinkled 
often enough to keep it thoroughly wet for 30 days. On April 11 
the contents were carefully examined and 35 live larvae and 90 dead 
larvae were found in the bolls and only 4 larvae and 2 pupae in the 
soil. Willcocks (7) found a very sudden increase in the number of 
larvas emerging to the surface in a box of bolls buried in dry soil and 
watered in the spring. 

Unfortunately a sufficiently large sample of bolls for our check 
was not examined at the beginning of the experiment to determine 
the mortality until this date, and the check sample examined at the 
end of the experiment contained more live larvae than at the begin- 
ning. The indications were, however, that the treatment had killed 
a large number of the larvae. The bolls were totally rotted and 
larvae which were dead at the beginning of the experiment were 
unrecognizable at the finish. 

MORTALITY OF HIBERNATEMG LARV^ IN STORED SEED. 

The number of larvae found in the ginned seed is very small com- 
pared to the number found in the bolls when the cotton is picked. 
In the Laguna the seed cotton is passed through cleaners or beaters 
before it goes to the gins to remove the trash and dirt. This causes 
most of the larvae to leave the lint and many are undoubtedly driven 
from the seed also during the process. Larvae are thrown out by 
the thousands with the trash that comes from the later pickings, and 
in some cases the pile of trash and the sides of surrounding buildings 



PINK BOLLWORM OF COTTON IN MEXICO. 



45 



are pink with crawling larviB. Many of the double seeds are torn 
apart in the cleaner and gin, though some go through unharmed. 
It is extremely disappointing to look for larvje in seed which comes 
from heavily infested cotton. In such seed in the winter or spring 
one can rarely collect more than 75 to 100 live larvae in the course of 
an eight-hour day. Ten samples of 2,500 seeds each were taken on 
different occasions during February and March, 1918 and 1919, 
from seed houses, examined seed by seed, and only 9 live larvae were 
fomid. 

For our rearing work larvae were removed by hand from the bolls 
and placed in fruit jars with seed to pass the winter. Table XXII 
shows that the mortality among larvae removed from boUs in No- 
vember and stored in the laboratory during the winter of 1918 and 
1919 was 22.6 per cent and that 0.4 per cent were stiU alive November 
20, 1910, when the work was discontinued. 

Other larvae were disturbed as little as possible and were left in 
the double seed where they had prepared to spend the winter. The 
double seed were picked from the lint by hand and stored in the 
laboratory under the same conditions as the othei*s. Table XXIII 
shows that there was 16.2 per cent mortality among larvae in double 
seed and that 4.4 per cent were stiU alive on November 20, 1919. 

Table XXII. — Mortality among larvx removed from bolls and kept in the laboratory in a 
condition as near to that of stored seed as possible. 



Date collected. 


Number 

entering 

resting 

stage. 


Number 
emerged. 


Per cent 
mortality. 


Per cent 
emerged. 


Number 

alive Nov. 

20, 1919. 


1918. 
Sept. 30 


83 
281 
256 
269 
260 
282 
309 
239 
320 
299 
277 
260 
244 
265 
125 


71 
191 
180 
153 
183 
220 
255 
201 


13.2 
31.6 
28.9 
43.1 
29.7 
22.0 
17.5 
1.5.4 


85.5 
68.0 
70.3 
56.9 
70.3 
78.0 
82.5 
84.1 
79.6 
81.6 
76.2 
74.2 
77.7 
91.3 
79.2 


2 
2 
2 




1 
2 
2 
1 
2 
1 
1 



Nov. 13 


Do 


Do 

Nov. 14 . 


Nov. 15 


Do 


Do 


Do 


255 19. 6 
244 17. 7 
211 23. 4 
193 25. 
192 20. 9 
242 8. 6 
99 1 20.8 


Do 


Do 


Nov. 16 


Do 


Nov. 17 


Nov. 19 


Total 


3,769 


2,890 






16 
0.4 per cent. 


22.6 


77.0 









The moths were removed daily and a record kept for each jar. 
The percentages used are based on the number of moths emerging 
and the number of dead and live larvae found in the jar at the end 
of the experiment. As these larvae were carefully removed by 
hand and stored indoors, the mortality was the minimum that can 
be expected and is much lower than in seed ginned and handled 
on a commercial scale. It is difficult to determine the mortality 



46 



BULLETIN 918, U. S. DEPARTMENT OF AGRICULTURE. 



in the seed warehouses, because the dead larvae are so hard to fiud, 
but it is evident to one collecting larvae that it is much higher in 
the early spring than in the fall. The mortality was 80 per cent 
among larvae thrown out by the cleaners and stored indoors during 
the winter, and in this sample only the most active larva* were used. 

Tab.le XXIII. — Mortality among larvae in double seeds removed from lint by hand and 
stored in jars in the laboratory. 



Date collected. 


Numljcr 

entering 

resting 

stage. 


Number 
emerged. 


Per cent 
mortality. 


Per cent 
emerged. 


Number 

alive Nov. 

20, 1919. 


1918. 
Nov. 15 


206 
190 

184 
88 
61 

213 

172 


182 
165 
157 
76 
41 
119 

143 


8.7 
9.4 
8.1 
9.0 
22.9 
41.3 

11.6 


88.3 
86.8 
85.3 
86.3 
67.2 
55.8 

83.1 


6 
7 
12 
4 
6 
6 

9 


Nov. 22 


Nov. 23 


Nov. 22 


Do 


Dec. 25 


1919. 
Jan. 23 


Total 

Average . . 


1,114 


883 






50 
4.4 per cent. 


16.2 


79.2 




1 



MORTALITY OF LARVi*; PLANTED WITH THE SEED. 

A screen-wire cage was built so that no infestation could interfere 
from the outside, and 100 dou])le seeds were planted with somid 
seed in 30 hills to see what the infestation would l)e from larvae 
planted with the seed alone. No infestation occurred during August, 
but from September 1 to November 7 the infestation went from 
12 per cent to 96 per cent, with an average of 5.6 larvae per boll on 
November 7. Thus it is evident that should all the larvae left in 
the fields be destroyed either naturally or by artificial means, the 
infestation arising from the larvae planted with the seed alone is 
sufficient to cause a considerable loss (Table XXIV) . 

Table XXIV. — Infestation of pink bollworm. from 100 double seeds planted in a cage. 



Datee.xamined. 


Per cent 
of bolls 
infested. 


Average infestation per boll. 


Larvae. 


Pupae. 


Exit holes. 


Total. 


1919. 
Aug. 1 








12.00 
84.00 
96.00 








0.12 

2.20 

5.60 


















0.96 










0.12 

3.16 

5.60 


Aug. 6 


Aug. 22 


Sept. 1 


Sent. 30 


Nov. 7 





PARASITES AND PREDATORS. 



What part of the mortality in the newly hatched larvae is due to 
starvation, exposure to the sun, or falling from the plants, and 
what to predacious insects, could not be determuaed, but the toll 



PINK BOLI^WORM OF COTTON IN MEXICO. 47 

taken by the nymphs and adults of three s])ecies of small mideter- 
mined Hemii)tera is evidently very high. The attacks on the 
small pink bollworm larvae from these predators are so important 
that daily examinations of all food placed in the breethng cages was 
absolutely necessary. Often one small nym])h would destroy the 
larvae from a large number of eggs during the night. 

The larva3 of a lace- wing, Ohrysopa rufilabils Burm., attacks 
the newly hatched pink bollworm and also the larger larvae in the 
flowers. 

Only very rarely is a dead larva found inside a boU. The feeding 
habits within the green l)oll greatly reduce the chances of attack by 
parasites and predators during this period. When the exit holes 
are cut, or the boll begins to open, or when the larva? are migrating 
to the ground, they are exposed to these enemies for a short time. 
This short period of exposure may accoimt for the very few parasites 
found. Only three sj^ecies and one specimen of each were found 
attacking the larva?. They were the Hymeno])tera Habrohnicon 
sp., Parisierola emigrata Rohwer, and a small dipteron, Tortri- 
ciophaga tortricis Coquillett. The scarcity of these jiarasites during 
the two yeare ])roves very conclusively that no relief can l)e ho])ed 
for from this source. 

The pupse of the pink boUworm in Mexico were not attacked by 
parasites, so far as our observations show. 

The small chalcid Tricliogramma minutum Riley may prove bene- 
ficial in parasitizing the eggs of the pink bollworm, but it was not 
observed attacking the eggs until late in the season, and then only 
very rarely. 

An outbreak of mites, Pediculoides ventricosus Newport, occurred 
on the hibernating larvse in the laboratory in 191S. Steps were 
taken immediately to check them by burning all infested material. 
To what extent these mites occur in the seed houses was not deter- 
mined. 

REPRESSION. 

FUMIGATION OF SEED. 

From the known instances in which infestations have occurred 
from larvae planted in the seed there can be no doubt of the danger 
of planting infested seed. Several methods of killing the larva? in 
the seed have been used in Egypt and other places {10), but all 
fall into three classes: Immersion of the seed in some substance to 
kill the larvae, treatment with heat, or furnigation with poisonous 
gases. Immersion of seed in liquids is obviously out of the question 
where tons of seed are used for planting on a plantation. In Egypt 
larvse can be killed by exposing them to the heat of the sun. Pre- 
liminary experiments showed that the temperature in Mexico during 
the planting season was not high enough to kill the larvae and that 



48 BTTLLETIN 918, U. S. DEPARTMENT OF AGRICULTURE. 

cotton seeds are very poor conductors of heat. Machines (4, 6) 
have been perfected for passing the seed on an endless belt through 
air heated to 130° F. and houses have (7) been constructed for 
heating a mass of seed sufficiently high to kill the larvae, but in 
Mexico fuel is scarce and very expensive, so fumigation with poi- 
sonous gases seemed the most economical and practical method 
to use. 

A fumigation chamber of adobe bricks set in mud, the usual type 
of building in the Laguna, was constructed. The walls of this 
chamber were about 20 inches thick and were plastered on the in- 
side and outside with cement. The floor was of brick set in mortar. 
During the fumigation the wooden door was closed and several 
thicknesses of wall paper plastered over the cracks. The size of the 
room was 5 by 8 by 10 feet, or 400 cubic feet. Tliree tons of cotton 
seed filled it about 5 feet deep. Experiments were made with seed 
placed in the room in bulk and in sacks. Carbon disulphid and 
hydrocyanic-acid gas were used. 

Carbo^j Disulphid. 

Live larvae, pupae, and adults were placed at different depths in 
the seed, usually near the top, center, and bottom of the pile. The 
use of adults was discontinued after the fu'st few experiments on 
account of the death of all the moths, while in the same experiments 
the mortality of the larvae varied a great deal. Pupae did not seem 
more difficult to kill than larvae. Larvae, and pupae when they could 
be obtained, were placed in single, double, and triple pill boxes, at 
least 60 larvae and sometimes more being used for each experiment. 
Larvae in double and triple boxes were thought to be about as diffi- 
cult to kill as larvae webbed up in seed would be. Sometimes the 
larvae would spin cocoons in the boxes before they were placed in the 
house, but such larvae were killed along with the others. Where 
only a few larvae were not killed they were always in the triple boxes 
on the bottom of the pile. 

As only one lot of 3 tons of seed was available, the seeds were 
taken from the house and left exposed to the sun for several days 
after each experiment. When the seeds were returned to the house 
the boxes of larvae were tied in a muslin bag and placed in position, 
the disulphid placed in shallow vessels on the top of the seed, and 
the door sealed. 

Considerable difficulty was experienced at first in determining 
whether larvae were dead or not. All of the larvae would appear 
dead when removed, but they still retained their pink color and some 
of them would revive and pupate after lying in a comatose state for 
a week or more. Later all the larvae were kept until we were abso- 
lutely sure whether they were dead or alive. Table XXV is a de- 



PINK BOLLWORM OF COTTON IN MEXICO. 



49 



tailed account of the fumigations that were made with carbon 
disulphid. 

Table XXV. — Preliminary fumigation experiments with carbon disulphid for P. gas- 
sy piella in cotton seed. 



Experi 
ment 
No. 



Dosage. 








Length 
of ex- 
posure. 


Poiuids. 


Ciiljic 
feet. 






Hours. 




102 


90 




l(il 


4S 




2S9 


4S 




101 


23 




161 


23 




161 


4S 




103 


4S 




124 


4S 




S2 


•IS 




54 


24 




SO 


42 




100 


1 week . 




100 


Ilour.t. 

4S 




SO 


4S 




SO 


4S 




so 


4S 




so 


24 




so 


12 




so 


ir. 




S.3 
S5 


24 

24 




90 
90 


24 

24 



How seed was 
stored. 



Location of larvae. 



9 
110 



In sacks.. . 

do 

do 

do 

do 

In1)ulk... 

do 

do 

do 

do 



In ba'.; 



In bulk 6 feet deep 



fTopsack 

\Bottom sack 

/Top sack 

\Bottom sack 

(Top sack 

\Bottoin sack 

fTopsack 

\Bottom .sack 

fTop sack 

\Bottom sack 

I'2h feet deep 

\4Afeet deep 

f2Jfeet deep 

\4Afeet deep 

f2i feet deep 

\4.Heet deep 

^2ifeet deep 

I4|-feet deep 

2h feet deep 

4J feet deep 

On top 

In center 

On bottom 

On top 

2 feet deep 

4 feet deep 

6 feet deep 

(isinchesfrom to: 

■^Middle ' 

iBottom . 
/Middle. 
IBottom . 
/Middle. 
IBottom . 
(Middle. 
IBottom . 

Bottom . 
/Middle. 
\ Bottom. 
(Middle. 
\Bottom . 
/Middle. 
\Bottom . 
/Middle. 
\Bottom . 

Bottom . 
do. 




100 



94 



iln Experiment No. 10 the larvse were placed in glass tubes, which were closed with cork stoppers, 
making them approximately air tight. 

In experiments 20, 21, and 22 all larvae were killed with 1 pound 
of disulphid to 80 cubic feet in 48 hours. In order to shorten the 
time, experiments 23, 26, and 27 were made, and all the larvae were 
not killed. All of the disulphid had not evaporated at the end of 
12 and 15 hours in experiments 26 and 27, but it had evaporated in 
experiment 23 in 24 hours, and all the larvae were killed, showing 
that 24 hours are necessary to evaporate and to secure maximum 
penetration of 1 pound of disulphid in 80 cubic feet. This was in 



50 



BULLETIN 918, U. S. DEPARTMENT OF AGRICULTURE. 



the summer time, when the temperature inside the house was 75° to 
80° F. Experiments 13, 19, 29, and 30 were made to decrease the 
dosage needed. All larvffi were not killed in experiments 13 and 19, 
where the dosage was 1 pound disulphid to 100 cubic feet with long 
exposures, but all were killed in experiments 29 and 30, with 1 
pound to 85 cubic feet and a 24-hour exposure. 

Table XXVI is a summary of the carbon disulphid experiments. 
From these experiments it is seen that satisfactory results were 
obtained by using 1 pound of carbon disulphid to 80 cubic feet for 
24 hours or longer when the seeds were not over 5 feet deep. 

Table XXVI. — Fumigation of cotton seed with carbon disulpJiid. 



Experi- 


Dosage. 


Expo- 
sure. 


Per cent 
larvae 
killed. 




ment 
No. 


Pounds. 


Cubic 
feel. 


How seeds were placed. 


1 

2 

11 

20 

21 

22 

23 

29 

30 

26 

19 

13 

10 

9 

31 

27 

7 

32 

6 

5 

8 

4 




102 
161 
80 
80 
80 
80 
80 
85 
85 
80 
100 
100 
54 
82 
90 
80 
102 
90 
161 
161 
124 
161 


Hours. 
90 
48 
42 
42 
48 
48 
24 
24 
24 
12 
48 
168 
24 
48. 
24 
15 
48 
24 
48 
23 
48 
23 


100 
1100 
100 
100 
100 
100 
100 
100 
100 

95 

94 

91 
2 90 

88 

85 

82. 5 

80.5 

60 

51 

37 

17 

13.3 


Seed in bags. 

Do. 

Do. 
Seed in bulk, 5 feet deep. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 
Seed in bulk, feet deep. 
Seed in bulk, 5 feet deep. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 
Seed in bags. 
Seed in bulk, 5 feet deep. 
Seed in bags. 



1 Record doubtful. 



2 LarviB in corked vials. 



Hydrocyanic- Acid Gas. 

The fumigation of cotton seed with hydrocyanic acid gas proved 
very unsatisfactory, as the gas is so light that it will not penetrate 
the seed more than a few inches. In some of the experiments an 
earthenware crock containing the sulphuric acid was set directly on 
top of the seed pile and the cyanid lowered by a string from the 
outside in the usual way. The penetration was so poor that a 
special generator was designed. A section of 10-inch pipe 14 inches 
long was fitted with gas-tight caps on both ends and a lead inner 
pot to hold the acid. The generator was placed outside the house 
below the floor level and the gas conducted to the inside, where it 
was allowed to escape in the bottom of the fumigation chamber 
through perforated pipes. It was hoped that the penetration 
upward would be greater than downward, but there was very little 
difference. 



PINK BOLLWORM OF COTTON IN MEXICO. 



51 



Table XXVII is a summary of the experiments with the use of 
hydrocyanic- acid gas. From these experiments it is seen that it is 
not practicable to use hydrocyanic-acid gas when the seeds are over 
4 inches deep. It could not be recommended even when seed is in 
ordinary bags, for the center of a bag of cotton seed is more than 
4 inches from the surface of the sack exposed. 

Table XXVI f. — Fmnigulion of cotton seed vith hydroajdnic-aeid gas. 



Experi- 
ment 
No. 


Position of generator. 


Dosage 

per 1(K) 

cubic 

feet. 


Expo- 
sure. 


Per cent 
oflarvi« 
killed. 


Remarks. 


17 


Inside . . 


2-2-4 
4-4-8 
2-2-4 
2-2-4 

4-4-8 

4-4-8 
2-2-4 
2-2-4 


Hours. 
2 
3 
2.1 
2' 
24 

24 

24 

48 


100.0 
70.0 
02.5 
60.0 
47.0 

34.0 

10.0 

. 6 


Seed in bulk, 4 inches deep. 


24 


do 


Seed in bulk, 6 incht>s deep. 


18 


do 


Do. 


2.5 


do 


Do. 


16 


. .do 


Seed in bulk, 5 feet deep; all not killed 


l.'i 


Outside 


6 inches deep. 
Seed in bulk, 5 feet deep; none killed 


14 


. . .do 


2^ inches deep. 
Seed in bulk, ih feet deep; all not 


12 


Inside 


killed 1 foot from floor. 
Seed in bulk, 5 feet deep. 









POISONING EXPERIMENTS. 

As a possible means of controlling the pink bollworm in the field, 
poison experiments were conducted in the laboratory with both 
adults and larva?. Moths readily drink water in captivity when ifc 
is sprayed on the leaves or blotting paper in the breeding jars, and 
it was thought they might be killed by poisoning the drinking water 
with an arsenical solution. Repeated trials were made by using a 
solution of calcium arsenate for the moths to drink. The longevity 
of these moths was the same as that of those in the check, where 
pure water was used. 

While the laboratory experiments in poisoning the adults were 
not encouraging, it was thought advisable to try it under field con- 
ditions. From the habit of the newly hatched larvse of crawling 
over the plants and bolls before they enter, theoretically it seemed 
possible that a large number of young larvae might be poisoned. 

Average plats wqyq selected at San Isidera, Tlahualilo, and at the 
laboratory for poisoning the plants. Weekly applications of pow- 
dered calcium arsenate were made with hand dusters. Tliese appli- 
cations were begun about July 15 and continued until the last week 
in October. The gauges on the machines were opened to their fullest 
extent and as heavv an application as possible was made each time. 
(Table XXVIII.) 



52 



BULLETIN 918, U. S. DEPARTMENT OF AGRICULTURE. 



Table XXVIII. — Weekly examination of bolls from poison experiments: Average num- 
ber of larvx per boll. 





Tlahualilo. 






Let 




Week ending— 


Zaragosa. 


Small experiment. 








Poison . 


f'heelv. 


Poison . 


Check. 


Poison . 


Check. 


Poison . 


Check. 


Aug. 2 


0. 05 

.11 

.20 

.31 

.57 

1.2 

1.8 

1.83 

1.45 

5.77 

6.40 

7.60 

7.20 

8.70 


0.13 

.09 

.23 

.38 

.88 

.86 

5.10 

1.50 

5.10 

6.90 

8.40 

8.10 

5.. 50 

9.80 


0.6 
.6 
.42 
.88 

1.2 

1.7 

2.3 

3.2 

1.2 

2.4 

4.0 

4.2 

6.0 

3.9 


0.66 
.44 
.40 
.32 

1.6 

3.0 

2.6 

2.6 

1.1 

3.4 

4.5 

5.0 

5.7 

4.0 






.02 

.04 

.02 

.14 

.20 

.25 

.27 

1.50 

3.70 

5.50 

8.00 

7.00 







.05 
.03 
.06 
.10 
.14 
.28 

2.30 

3.0 

5.30 


0.02 
.SO 
3.50 
4.34 
4.16 
2.8 
4.6 


0.62 


Aug. 9. . . 


.80 


Aug. If. 


3.88 


Aug. 23 


3 14 


Aug. 30 


3.52 


Sept. 6. . 


2 7 


Sept. 13 

Sept. 20 


4.8 


Sept. 27 


6.28 


5.84 


Oct. 4 




Oct. 11 






Oct. IS 


6. 48 




Oct. 2,1 




Oct. 31 


5.10 


5.70 


5.00 











Weekly examinations of bolls both from the poisoned and check 
plats were made. The average number of larva> per boll varied 
slighth'. These variations, however, occurred in other samples of 
bolls where no poison was used and the poisoning did not check the 
infestation. Tlie season of experiments was unfavorable for poison- 
ing experiments. Tliere w^as about twice the normal rainfall, which 
washed the poison from the plants, and, moreover, caused the cotton 
to grow so rank that it was impossible to get a thorough application 
with the available labor. Under more favorable conditions it is pos- 
sible that better results might be obtained. 

TRAPS. 

Trap Lights. 

In the laboratory, where the doors and w^indows were screened and 
the moths could not escape, they would frequently come to the elec- 
tric lights, resting on the shade or wall near by, but under outdoor 
conditions moths would seldom come to lights. Acetylene and elec- 
tric lights were suspended repeatedly in front of a white background 
in the laboratory cotton plats, w^here there were thousands of moths. 
In the course of 2 or 3 hours not more than 6 to 8 moths would 
come to the lights, while at the same time an examination with a 
flashlight would show there were large numbers on the plants only a 
few feet away. The few that did come to the lights were probably 
ones that we distur])ed in moving about, and it can not be said there 
was any attraction whatsoever to the lights. 

An electric trap light was also placed within a few feet of the plants, 
with negative results. Another trap light was run all night for 15 
consecutive nights in an open shed where there were hundreds of tons 
of seeds and only 5 moths were taken. During: the same 15 nights 



PINK BOLLWORM OF COTTON IN MEXICO. 53 

large numbers of moths were emerging from material at the labora- 
tory which had been taken from this same shed a few weeks before, 
and it is certain that large num])ers of moths were emerging in the 
seed shed while the. trap was in operation. Light traps have been 
recommended as a means of control b}- several people. Gongh (13), 
Willcocks (7), Ballon (11), and others report catches of thousands of 
moths per night in light traps. Ballou (11) found that most of the 
moths came to the light in the hour following sunset. Some authors 
found lights so attractive to the moths that they were used to deter- 
mine the number of moths emerging from stored material, but in 
Mexico we found that practically none came to the lights. Busck (8) 
in Hawaii also found that the pink ])ollworm moths were not at- 
tracted to lights. 

Attraction to Frcit. 

Cone-shaped traps of the type used for flies were baited with 
oranges, bananas, apples, mangoes, guavas, and pineapples and were 
repeatedly exposed among the cotton plants with absolutely negative 
results. 

RECOMMENDATIONS FOR CONTROL. 

Too much can not be said and done in eiicoiu-aging the destruction 
of hibernating larvjp. They are the source of infestation for the fol- 
lowing year. If 9 per cent or less of the larvte are able to sur- 
vive the natural mortality of winter and early spring in irrigated 
fields, this small percentage, with the larva? surviving in the seed and 
other places, produces an infestation the following year that causes 
approximately 25 per cent gross loss to the Laguna crop. Every 
hibernating larva killed during the winter or early spring before 
oviposition begins means the cutting off of many thousand larvie by 
the end of the season. The paramount necessity, then, is to re- 
duce the survival of hibernating larvae to as low a figure as possible. 

Burning of Old Stalks and Bolls. 

Just as soon as possible the stalks should be cut and raked up in 
piles. Old bolls, sticks, and trash of all descriptions to which larvae 
may be attached should be carefully picked up and burned with the 
the stalks, the main object being to burn everything in the field that 
contains larvae or would be likely to afford protection for hibernating 
larvse. If possible, the cutting and piling of the stalks should be done 
wliile the plants are still green, in this way minimizing the labor and 
increasing the effectiveness of the operation. Green stalks will 
retain most of their bolls, which shatter when they are cut dry. Just 
as soon as the piles lose their green color and become more or less 
dry they should be burned. Better results can be gained by waiting 
for this ckying to take place rather than by burning the plants while 
they are yet green. Ordinarily the old stalks are cut and burned in 



54 BULLETIN 918, U. S. DEPARTMENT OF AGRICULTURE. 

the Laguna when preparing the land for the new crop. While this is 

done for piu'ely agricultural reasons to make plowdng easier, large 

numbers of live hibernating larvse are killed. On the experimental 

plot at Lerdo the stalks were cut on the last day of February and 

examined during March. *At tliis examination live larva? at the rate 

of over 5,000 per acre were found in the bolls attached to the stalks. 

So many bolls had fallen or were knocked off during the cutting and 

piling that over half were left on the ground. A little extra effort in 

collecting and destroying these is well worth while. No boll or piece 

of cotton is so small or negligible that it should not be picked up and 

burned. 

Cutting Stalks and Fall Plowing. 

Experiments have shown conclusively that the mortality is greater 
in hibernating larvae buried in the soil than in those left on top of the 
soil and greater in those buried in irrigated soil than in those buried 
in dry soil. It has also been found that the most favorable of all 
places for larvae to hibernate under field conditions are the old bolls 
left undisturbed on standing stalks. DMring the winter of 1919-20 
100 larvae per 100 bolls successfully passed the winter on old stalks 
left standing in the fields and were alive on July 12, whereas only 4 
larvae per 100 bolls were found alive on this date in bolls lying on top 
of the soil. These facts suggest certain agricultural practices that 
can be used to good advantage in reducing the number of surviving 
larvae. 

Ordinarily the old stalks are not left standing in the fields, but on 
some plantations large acreages which are not to be cultivated the 
following year are left, and on others where "zoca" is produced the 
stalks are not cut till late spring or summer. All fields should be 
gone over with a stalk-cutter as early as possible, and in many cases 
the small amounts of cotton wliich are picked during the winter 
and spring could profitably be sacrificed in order to do this earlier in 
the season. Fall and winter plowing to cover the bolls is recom- 
mended whenever it is possible, and water should be applied in years 
when there is an excess. 

Pasturing. 

If it is not possible to cut and burn the stalks or plow the field in 
the above manner, owing to labor shortage, weather conditions, or 
other causes, it is a very good idea to graze the fields. Cattle, goats, 
and burros will eat the majority of the bolls on the stalks. One 
important drawback to the grazing plan is that there is a certain 
amount of infested material tramped into the ground. In one field 
near the town of Tlahua'ilo where the animals had been concentrated, 
only about one boll per square yard was fountl on the ground. In 
other fields that had been grazed, but not so thorouglily, an average 
of 5 or 6 bolls per square yard was found. 



PINK BOLLWOEM OF COTTON TTST MKXTCO. 55 

Cleaning Gins, Oil Mills, and Seed Warehouses. 

In Mexico, whore the infestation grows to be very intensive, thou- 
sands of live larvae have been observed to come from the cleaners with 
the trash. It is the common practice there merely to collect this 
trash containing the large number of worms and place it in piles. 
The "cleanings" should be caught in a receiDtack^ rather than allowed 
to faU on the ground, because the larvae will crawl and secrete them- 
selves in cracks, crevices, and rubbish of various kinds. This trash 
should be either burned or subjected to some tn^atminit insuring the 
death of the insects contained therein. If the trash does not contain 
too much dirt to make it unburnable, the best plan is to burn it in the 
boilers. A very good plan was devised by Mr. T. M. Fairbairn foi 
handlino; the unburnable material. The end was knocked out of 
an oil barrel and a small steam line run into the barrel, almost to the 
bottom. The trash from the cleaners fell into the steaming barrel 
and all larvae were quickly killed. 

After the season is over the gin plant or oil mill should be thor- 
oughly cleaned. All seed and rubbish should be removed from every 
nook and crevice of the machiner}^ and buildings and burned. If 
the structure of the buildmgs permits they should also be fumigated 
after cleaning. 

• It is the usual custom to keep enough seed on the plantations for a 
second planting in case it is necessary. This s(ied should be as care- 
fully fumigated as the seed that is planted, and as an additional pre- 
caution should be stored in a moth-proof screened room. It was very 
noticeable that the infestation always began earlier in the season 
and was heavier in the fields nearest the gins and seed wai'chouses. 

Fumigation. 

All seed used for planting or kept on the plantation after the 
first of March should be fumigated. An air-tight room is necessary 
for a successful fumigation, and it is better to build a special fumi- 
gation house at least a hundred yards from the other buildings, so 
that there will be no danger from the. Carbon bisulphid is highly in- 
flammable, and no fire should be allowed around the house while 
fumigation is being done. The ordinary adobe construction is 
satisfactory, but precautions should be taken to see that plenty of 
mud is used and all cracks between the adobes well filled. A brick 
floor set in mortar should be provided and the inside plastered. The 
plastering not only makes the building more air-tight, but prevents 
absorption of the gases by the walls. The doors should be of matched 
wood, and paper should be' plastered over the cracks when closed. 
Seed may be fumigated in sacks or in bulk, but in either case should be 
packed as little as possible. In no case should the seed to be fumigated 
be over 5 feet deep. One pound of carbon disulphid should be used 



56 BULLETIN 918, U. S. DEPARTMENT OF AGRICULTURE. 

for every 80 cubic feet. The entire area of the building should be 
calculated and not the space occupied by the seed only. As it costs 
as much to fumigate the air space as it does the seed, it is more eco- 
nomical to make the room only high enough for a person to stand 
comfortably. The size of the building needed can be calculated 
from the tons of seed to be fumigated, a ton of seed occupying 85 
cubic feet (2^ cubic meters). 

All water should be separated from the carbon disulphid and after 
the seed is in the house the disulphid poured into shallow vessels 
placed on top of the seed. Not more than a pound should be placed 
in each vessel, so that it will evaporate quickly. Old gasoline cans 
cut down to about 3 inches high, or earthenware bowls, make good 
containers. The vessels should be scattered over the top of the 
seed pile and the disulphid poured into those farthest from the door 
first. There is no danger in doing this, but it is more convenient to 
have a number of half-inch pipes fitted with caps or corks extending 
through the walls and introduce the disulphid from the outside. As 
soon as the liquid is poured into the vessels the door should be closed 
and paper stuck over the cracks with flour paste. The house should 
be kept closed for at least 24 hours, and longer will do no harm, as 
continued exposure to the gas does not injure the germination of the 

seed. 

Planting Early Varieties. 

From the life history and feeding habits of the pink bollworm it 
can be readily seen that the later the cotton crop is in maturing the 
greater will be the amount of loss. Every cultural practice should 
be used in securing as early maturity as possible of the available 
cotton varieties. 

SUMMARY. 

The pink bollworm was introduced into Mexico in 1911 with seed 
for planting. Five years later it was generally and uniformly dis- 
tributed throughout the Laguna and had reached its maximum 
development. 

Infestation is started in the spring as soon as squares are formed, 
by moths emerging from hibernating larvae, and rapidly increases 
until practically every boll is infested with several larvse by fall. 

The life cycle is completed in an average of 31 days in the summer, 
but the larval stage of hibernating or resting larvae may be extended 
for 2 years or more. 

Dispersal is mainly through the carriage by man of hibernating 
larvae in seed, but local dispersion is brought about also by flight and 
carriage of adults. 

The pink bollworm causes approximately 25 per cent gross damage 
to the Laguna crop by feeding in the bolls and squares. This feeding 
results in a reduction in the quantity and quality of the lint pro- 



PINK BOLLWORM OF COTTON IN MEXICO. 57 

duced, reduction in the quantity of seed, and lowering of the quantity 
and quality of the oil content of the seed. 

Early cleaning of fields by burning all the old stalks and bolls, 
cleaning and fumigation of gins, oil mills, and seed warehouses, the 
fumigation of all seed kept on the plantations, and the early maturity 
of the crop are recommended as means of control. 

LITERATURE CITED. 

(1) Hinds, W. E. 

1906. proliferation as a factor in the natural control of the mexi- 
CAN COTTON BOLL WEEVIL. U. S. Dept. Agr., Bur. Ent. Bui. 59. 45 
p., 6 pi. 

(2) Maxwell-Lefroy, H. 

1906. INDIAN INSECT PESTS. 318 p., 346 figs., and figs. A-S. Calcutta. 

(3) FULLAWAY, D. T. 

1909. INSECTS OF COTTON IN HAWAII. Hawaii Agr. Exp. Sta., Bui. IS. 27 p., 
18 figs. 

(4) GouGH, L. H., and Story, G. 

1914. METHODS FOR THE DESTRUCTION OF THE PINK BOLL WORM (c.ELECHIA 
GOSSYPIELLA, SAUND.) IN COTTON SEED. //( AgT. Jour. Egypt, V. 3, 

pt. 2, 1913, p. 73-95, 5 pi. Ministry Agr., Cairo. 

(5) GouGH, L. H. 

1916. THE LIFE HISTORY OF GELECHIA GOSSYPIELLA FROM THE TIME OF THE 
COTTON HARVEST TO THE TIME OP COTTON SOWING. Ministry AgT. 

Egypt, Tech. and Sci. Serv. Bui. 4 (Ent. Sect.). 16 p. 
(6) 

1916. NOTE ON A MACHINE TO KILL GELECHIA LARV^ BY HOT AIR, AND THE 

EFFECTS OF HEAT ON GELECHI.\ LARV^ AND COTTON SEED. Ministry 

Agr. Egypt, Tech. and Sci. Serv. Bui. 6 (Ent. Sect.). 18 p., 3 pi. 

(7) WiLLCOCKS, F. C. 

1916. THE INSECT AND RELATED PESTS OF EGYPT. V. 1. The iiisect and re- 
lated pests of the cotton plant, pt. I. The pink bolhvorm. Sul- 
tanic Agri. Soc, Cairo. 339 p., 17 figs., 10 pis. 

(8) BuscK, A. 

1917. THE PINK BOLLWORM, PECTINOPHORA GOSSYPIELLA. In U. S. Dept. 

Agr., Jour. Agr. Research, v. 9, no. 10, p. 343-370. 12 pi., 7 figs. 

(9) King, H. H. 

1917. THE WEED HANBUK (ABUTILON SPP.) AND ITS RELATION TO THE COTTON- 
GROWING INDU.STRY IN THE ANGLO-EGYPTIAN SUDAN. Ent. Bul. 7. 

4 p. Khartoum. 

(10) Story, G. 

1917. machines for the treatment of cotton seed against pink boll- 
WORM (GELECHIA GOSSYPIELLA SAUND.). Ministry Agr. Egypt, Tech. 
and Sci. Serv. Bul 14 (Ent. Sec). 29 p. 

(11) Ballou, H. a. 

1919. COTTON and the PINK BOLLWORM IN EGYPT. Pts. I and II. In 
West Indian Bul., v. 17, no. 4, p. 237-292. 9 figs. 

(12) GouGH, L. H. 

1919. ON THE EFFECTS PRODUCED BY THE ATTACKS OP THE PINK BOLLWORM 

ON THE YIELD OF COTTON SEED AND LINT IN EGYPT. Bul. Ent. Re- 
search, v. 9, pt. 4, p. 279-324. 



APPENDIX. 



The following generic and specific description is reprinted from 
''The pink bolhvorm, Pfctinophora gossypiella,'' by August Busck, 
Journal of Agricultural Research, vol. 9, no. 10, Washington, D. C, 
June 4. 1917. 



HOW TO DISTINGUISH THE PINK BOLLWORM IN THE FIELD. 

Definite and final determination of P. gossypieUa in any stage can be made only by 
the aid of the microscope; and, unless a collector or inspector is thoroughly familiar 
with the species, all suspected material should be sent at once to the Bureaxi of 
Entomology for determination. Even a fraction of the insect in any of its stages can 
be recognized under the microscope by the characters given in succeeding sections 
of this paper. 





'//..'i-ji'' } 



\f t-^ If" 







''-■'My 



I 



> 



Fig. 1.— Pink bollworm: Adult. (Busck.) 



The following essential characters, all of which can be discerned by the aid of a 
common pocket lens, will enable the practical worker to make a reasonably certain 
preliminary determination of the insect in all its stages in the field. 

If a small dark-brown moth is caught in the cotton field or in a cotton mill or ware- 
house and is found to have the fore wings pointed and the hind wings broad and sinuated 
below the tip and to ])0ssess long curved palpi and long stiff hairs on the first antennal 
joint, it is reasonably certain that the moth is /'. gossypieUa, the adult of the pink boll- 
worm (fig. 4, ^-1). 

If, within the cotton l)oll or associated with stored cottonseed, a small white or 
])inkish caterpillar with brown head is found and under a hand lens the mandibles are 
■ 58 



PINK BOLLWORM OF (COTTON IN MEXICO. 



59 



seen to have four teeth (fig. 5, A-D) and the crotches on the abdominal prolegs form a 
partial circle or horsehoe, opening outwards (fig. 5, //), the caterpillar will most 
probably prove to be the pink boUworm. 

Again, if, within a cotton boll or otherwise associated with cotton in the field or in 
the mill, a small lepidopterous pupa is found, which under the lens is found to be 
entirely covered with a short velvety pubescence and to possess a short, curved, up- 
turned hook at the posterior end (fig. 0. A-D). it may with considerable certainty be 
determined as a pupa of the pink boUworm. 




Fig. 5.— Pink bolKvorin: A, Right mandililr of larva from undorsidc. B, Left iiiandilile frnni iiiidcrsidp. 
C, Ristit niandililc from uppor sido. 1), Left, niandilile from iijipor side. A', Loft antenna of larva from 
nndersidi : J, First joint; s', sccimd joint: .i, third joint; 4. f"i"'"i j<'i"t- /•', Epipharynx of larva: ES, 
Epipharyngeal shield; iT T, eiiipharyngcal sola; r, epipharyngeal rod. G, Labrum of larva: Lai, 
Lateral labral .seta 1; La^, lateral labral seta 2; L03, lateral labral .seta 3; ,1/1, median labral seta 1; Ah, 
median labral seta 2; JI/3, median labral seta 3; p, labral pimctures; r, epijjharyngcal rod. //, lenders uli: 
of third abdominal segment of larva. (Busck.) 

GENERIC DESCRIPTION. 

Pectinophora, new genus (Gelechiida'). 
Type: (Idechia gosi^ypirlla Saunders. 
Moth. — Face and head smooth. Labial palpi long, recurved . reaching al)ove vertex ; 
second joint thickened on the underside with slighUv furrowed l)rush, which is evenly 
attenuated toward apex; terminal joint shorter than second, somewhat thickened 
with scales in front, compressed, pointed. Maxillary palpi minute, deflected. 
Tongue long, spiraled, scaled in its entire length. Antennte serrated and finely cili- 
ated on the underside; basal joint with heavy but sparse (5-6) pecten. Thorax 
smooth. Forewiugs (fig. 7, ^1) elongate ovate, pointed, smooth; 12 veins, 7 and 8 



60 



BULLETIN 918, IT. S, DEPARTMENT OF AGRICULTURE. 



stalked to costa, rest separate, lb furcate at base." Hind"wings (fig. 7, B) somewhat 
broader than forewings, trapezoidal; costa deflected from the middle; apex pointed; 
termen sinuate; 8 veins; 8 connected with cell by an oblique bar: 6 and 7 closely 
approximate at base; 3 and 4 connate; 5 parallel with 4; frenulum simple in the 
males, triple in the females. Male genitalia (fig. 9, B), with harpes and uncus well 
developed; tegumen evenly chitinized. Posterior tibia? (fig. 9, A) hairy above. 

Larva.^ — Head (PI. V and fig. 8) spherical, nearly circular in outline viewed from 
above, a little wider than long; greatest width a little behind the middle; incision 
of dorsal hind margin about one-fourth of the diameter of the head ; distance between 





Fig. 6.— Pink bollworm. ^4 , Pupa from front: Z6, Labrum; /, front; c. clypeus; <?, gena; wd, mandibles; 
ge, glaced eye; e, eye; mp, maxillary palpus; mi, maxilla; h, first tnoracic leg; l2,_ second thoracic leg; 
/s, third thoracicleg; n, antemia; w, forewing; ffo, genital opening; ao, anal opening, i?. Tip of pupa 
from left side: c, Cremaster. C, Mature pupa, with eyes of the imago visil)le I hrough pupal skin. I), Pupa 
from back: f, Front; v, vertex; /i, first thoracic seginent; h, second thoracic segment; is, third thoracic 
segment «i, first abdominal segment; os, second abdominal segment; qs, third abdominal segment; 04, 
fourth abdommal segment; as, fifth abdominal segment; a^, sixth abdominal segment; n?, seventh 
abdominal segment; as, eighth abdominal segment;' fig, ninth abdominal segment; Ojo, tenth abdominal 
segment. (Busck.) 

dorsal extremities of hind margin about one-half of the width of the head. Front 
triangular, reaching beyond the middle; adfrontal sutures somewhat undulating, 
reaching to the incision of hind margin; adfrontal ridges converging from near the 
middle, at the point of attachment of tentorial arms, to the longitudinal ridge, which is 
one-half as long as front. Projection of the dorsal margin over the ventral is one-half 
of the diameter of the head. Triangular plates of hypostoma distinctly separated by a 
slightly pigmented gula, nearly e(|uilateral, but somewhat elongated and projecting 
slightly beyond the ventral margin of epicranium. 

Ocelli six; i, ii, v, and vi forming a parallelogram; iii and iv on a line between ii 
and v; v smaller than the rest.^ Epistoma Avith the usual two pairs of setse (E,, Eg) 
well developed. 



6 The European (Gckckia) Pcctinovhnra vialvcUa Zeller exhibits an amount of variation of the venation 
in the forewing which is very unusual in this group of insects. Veins 2 and 8 in this species are sometimes 
coincident or partly coincident at base or at tip; the variations sometimes differing in the two wings of the 
same insect. No such variation has been ascertained in P . gossypklla, wiiere the venation seems constant, 
as given above. 

' This numbering of the eyes differs from that of Fracker in that his numbers 5 and 6 are reversed, so as 
to make them continuous with the rest. (Fracker, S. B. The Classification of Lepidopterous Larvae . . . 
169 p., 10 pi. Urbana, ill., 1915. Bibliography, p. 145-146. Illinois Biological Monographs, v. 2, no. 1.) 



Bui. 918, U. S. Dept. of Agriculture. 



Plate V. 




PINK BOLLWOEM OF COTTON IN MEXICO. 



61 



Frontal punctures (Fa) close together, anterior to frontal 8et?p (F,); distance between 
punctures less than distance between puncture (Fa) and setae (Fj); frontal sette (F,) 
and adfrontal sette (Adfj and Adf^) nearly equidistant; second adfrontal seta (Adfj) 
approximate to but before beginning of longitudinal ridge (LR); adfrontal puncture 
(Adfa) midway between adfrontal seta\ 

Epicranium with normal number of primary seta^, 13, and inmctures, 7, and with 
three small ultra posterior pujictures * (x, y, and z).^ 

Anterior set;e '" (Aj, Aj, Ag) in a slightly obtuse angle; Ai and Aj closer together 
than Ao and A3; anterior pimcture(Aa) between A, aiid Aj. Posterior seta-'^ (P,, F^) 
and posterior })unctures (Pa, Pb) near the middle of the 'head; Pi on the level with 




B 

Fig. 7.— Pink bollvvorm: .4, Veiiatiou of forewiiig: B, venation of hindwing. (Biisck.) 

adfiontal puncture ^-■, P, jxisterior to AdL^. Pa eqiudistant from Pj, A3 ami the lateral 
seta (Lj) remote from the anterior group, nearly on the level with P;; lateral seta (L,) 
remote from A3, nearly on the level of Pb ; lateral puncture (La) postero ventral to the 
seta, remote. __ Of the ocellar seta? (Oj, Oo, O^),'^^ Oj is equidistant from and lateral to 
ocelli ii and iii, O., is closely approximate" and posteroventral to ocellus i ; O3 is directly 
ventral and remote from O,, on a line with ocelli v and vi; ocellar puncture (Oa) be- 
tween O3 and ocellus \i, a]iproximate to latter. Subocellar setae (So,, So,, 803) 
triangularly ])laced, nearly ecjuidistant; subocellar puncture (Soa) between and equi- 
distant from Soo and S03. (ienal seta (Gi) and puncture (Ga) both present; pujicture 
anterior to seta. 

Labrum (tig. 5, F, G) with mediaai incision rather deep and evenly rounded. The 
three lateral seta? (La„ La,, Lag) close to edge, Laj and La., closely approximate, 
Lag remote; median setae (M,, M2, M3) in the usual Micro arrangement with M, lateral 
and slightly posterior to M,; M3 close to anterior margin on a line wdth La3;"Mi and 
Mo on a line respectively with Lag and La,. 



8 The nomenclature of the head setir has been adopted from Heinrich [Heinrich, Carl. On the taxonomic 
value of some larval characters m the Lepidoptera. In Proc. Eut. Soc. Wash., v. IS, no. 3. p. 154-1(1-1, illus. 
191ti.] with certam minor modifications, noted in the following footnotes and concurred in b.v M; . Heinrich. 

sSo-called "secondary innutures" of Heinrich. sometimes bearing mmute seta-. 

1" .Vnterodorsal set :!■ of Iloinrich. 

" Posterodorsal set a' of Heinrich. 

12 The term "on the level w iih " is used in these descriptions as the head set:5e are seen infrontal projec- 
tion ( PI. V, ^); anyi hing alsove a level is termed "posterior" and anything below is termed "anterior." 

13 Hemnch's numbering reversed. 



62 



BULLETIN 918, U. S. DEPAKTMENT OF AGEICULTURE. 



Epipharyngeal shield (ES) merely a slight chitixiization of the edge of the median 
incision; epipharyngeal sette narrow plates, triangularly grouped near anterior margin. 
Epipharyngeal rods not discernible in the labrum proper, only represented by their 
posterior projections, which are rather well developed. 

Mandibles (fig. 5, A-D) strong, as broad as long, with four stout, rather short teeth: 
the three lower ones pointed; the upper blunt; a fifth lower tooth is slightly indicated 
on the underside; one long and one shorter .seta on upjter side near lower edge. 

Labium and maxillse normal (fig. 8, C). 

Antennae (fig. 5, E) four-jointed, with second joint considerably longer than joint 
3, longer than broad; the longer seta longer than the entire antenna; papillae minute, 
much shorter than third joint. 

Three i>airs of normal thoracic feet; four pairs of abdominal prologs with crotches 
of uniform size in aji incomplete circle, opening outwardly (fig. 5, //); anal prolegs 
with a transverse row of uniordinal hooks. 

The arrangement of the body setaj is normal, as shown in figure 10, A, B. It differs 
from that of Gelechia in ha^'ing the three setje on prespiracular plate of prothorax 
nearly equidistant, while in Gelechia the posterior seta is farther separated from the 
two othera than they are from each other, and in having the three setfe \'ii of the 
proleg-bearing abdominal segments arranged in a triangle, not in a line as in Gelechia. 




sp Ip I 

r. I I 




Fig. 8.— Pink bollworm. A, larval head from underside. B, Seta arrangement of epicranium in figure A: 
/, Ocellus i; //, ocellus ii; III, ocellus iii; IV, ocellus iv; V, ocellus v; VI , ocellus vi; Oi, ocellar seta 
1; O2 ocellar seta 2: O3, ocellar seta 3; Oa, ocellar puncture; S0\. subocellar seta 1; S0«, subocellar 
seta 2; SO3, subocellar seta 3; SOa, subocellar puncture; Gi, genal seta; Ga, genal pimcture. C, La- 
bium and maxilla:-: sp, Spinneret; Ip, labial palpus: I, lacinia and galea; m, mentum; sm, submen- 
tum; cr, cardo; st, stripes; p?^, palpiger; wipi, ma.xillary palpus, first joint; mpj, maxillary palpus, sec- 
ond joint; mpi, maxiUary palpus, tfiird joint. (Busck.) 

The genus differs further from Gelechia in the possession of an antennal pecten in 
the moth, and in the arrangement of the setfe of the larval head; Aa is anterior to Aj, 
not posterior to it as in Gelechia; Pj and Pj are posterior, respectively, to Adfj and 
Adf.„ which in Gelechia are nearly opposite to these, and Li is posterior to Pj, not 
on the level with it as in Gelechia. 

The most striking larval difference is in the crotches of the abdominal prolegs, which 
are uniordinal and arranged in an incomplete circle, broken outwardly (fig. 5, K). 
In Gelechia they are biordinal and in a complete circle. 

Pupa. — The pupa of Pcctinophora gossi/piella is pubescent, without any long setae 
except on last joint, and thus is easily distingui-shed from the smooth, seta-bearing 
pupa of Gelechia; cremaster present. 

SPECIFIC DESCRIPTION. 

Moth (fig. 4, J.).— Labial palpi reddish brown; second joint with two diffused black 
bars exteriorly; terminal joint with two well-defined, broad, black annulations, onfe 
at base, the other at apical fourth. Antennae brown ^vith narrow black annulations; 



PINK BOLLWOEM OF COTTON IN MEXICO. 



63 



basal joint with Ions; black pecteii. Face and head li.oht reddish brown with some 
pale iridescent scales. Thorax reddish brown with a s])rinkling of black around the 
collar; patagia somewhat lighter brown, unmottled. Forewings darker brown with a 
series of small, ill-delined, black spots along the costal edge from base to apical fourth, 
where there is a larger dash of light ocherous brown; dorsal edge and apical part of 
wing suffu.sed v.i.ih darker, blackish brown; the middle of tlie wing is irregularly 
sprinkled with blackish scales and contains on the cell an ill-delined, round, blackish 
spot, sometimes divided into an upper and lower spot; there is also a smaller spot on 
the base of the cell; the pattern of the wing is rather vague and there is considerable 
variation in different specimejis; in many tliere is an ill-deiined blackish fascia at 
apical fourth just before the light costal dash, but in other specimens this fascia is 
not present and the round dorsal spot is dissolved into several smaller spots. Cilia 




Fig. 9.— Pink bollworm: A, right hind leg. B, genitalia of male: u. Uncus; t, tegumen; //, haip; n, 
podceagus; s, sacculus. C, genitalia of female: o, Ovipositor; g. genital jilate with genital opening; 
db, ductus bui'sae; ds, ductus seminalis; 6c, bursa copulatrix. (Busck.) 

light ocherous brown, streaked with blackish. Hindwings dark fuscous, somewhat 
iridescent, lightest toward base; cilia ocherous, terminal and apical parts suffused 
with dark fuscous: vein Ic with long, ocherous fuscous hairs on the upper side. 
Abdomen flattened and ocherous above, dark brown laterally with underside suffused 
with black and with ocherous scaling at the joints. Legs (tig. 9, A) blackish fuscous 
with narrow ocherous annulations at the joints. The abdomen is very similarly 
shaped in the male and in the female and it is exceedingly diffictdt to distingidsh the 
sexes, even in li^'ing moths, without dissection or by examination of the frenulum. 
The male genitalia (fig. 9, B) are remarkaldy small in proportion to the size of the 
species: harpes narrow at base, broadenijig towards tip; tip strongly haired; a 
cluster of long, hea\y, straight spines from inner side, well within the tip; sacculus 
armed on its edge with a row of stout spines; luicus moderately long, broad at base, 
tapering to a point, laterally heavily haired; a'do^agus short, stout, with a terminal 
hook. In the female the ovipositor is weakly chitinized, covered with stii^ hairs; 



64 



BULLETIN 918, U. S. DEPARTMENT OF AGRICULTURE. 



genital plate heart shaped; bursa copula trix w-ith two opposite, strongly (^hitinized, 
hornlike, serrated invaginations (fig. 9, C). 

Alar expanse 15 to 20 mm. 

Full-grown LARVA.- -The full-grown larva (fig. 10, A) is 11 to 13 mm. long, 
cylindrical, white, with dorsal side strongly suffused with pink. He-^d reddish brown 
with blackish brown mandibles and the other trophi yellowish. Thoracic shield 
rather small, divided in the middle, dark brown. [On each side of the thoracic shield 
is a small, slightly depressed, kidney-shaped spot, thinly chitinized and less pig- 
m.ented than the rest of the shield. This purely specific character is easy to observe 
and may be of some assistance as contributory e\ddence in a preliminary determina- 
tion of the pink bollworm in the field ((ig. 11).] Anal plate small, dark brown. 





Vf 




TZM 



AH 



AT 



B 



Fig. 10.— Pink bollworm- A, larva. B, schematic chart of arrangement of body setse of larva. TI, 
first thoracic segment; T II, III, second and third thoracic segments; A ///, "third abdominal seg- 
ment; A K///, eighth abdominal segment; A IX, ninth abdominal segment; A AT, tenth abdominal 
segment. (Busck.) 

Tubercles small, but distinct, yellowish l)rown, surrounded by deeper pink than the 
prevalent suffusion and bearing rather short, dark-brown setae. Crotches of abdom- 
inal feet 15 to 17. 

Pupa.— The pupa (fig. 6, A-D) is 8 to 10 ,-<""""'Y^ 

mm. long, rather plump, reddish brown; ., •' \ / ^■••■••... 

posterior end pointed and terminating in a / \ / "'^ 

short, stout, upwardly turned hooklike ere- / \ J \ 

master; entire surface finely pul)escent; no I y I 

long set*, spines or hooks, except on last 
joint; fronto-clypeal suture distinct and 
curved sharply upward; clypeus, labrum, 
pupal eyes and mandibles distinctly indi- 
cated; antennae diverging at their extreme 
tip and not reacliing to the tips of the 
wings; metathoracic legs reaching slightly 
beyond the wings to fifth abdominal segment. 
Spiracles small, normal. Anal opening 
large, slitlike, surrounded by strong hooked 
setae, 5 or 6 on each side; cremaster sur- 
rounded with 6 to 8 similar, strong, hooked 
setae. Genital opening slitlike, single in 
both sexes. When mature, the pupa be- pj^^ n 
comes much darker (fig. 6, C); the imago's 
eyes can be seen prominently under the 
gena of the pupal skin, and the segmentation of the adult antennae and legs becomes 
discernible. 

o 




-Thoracic shield of pink bollworm 
larva. (Original.) 



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